We report the synthesis and systematic studies of a new layered ternary telluride ${\mathrm{TaPdTe}}_5$ with quasi-one-dimensional ${\mathrm{PdTe}}_2$ chains. This compound crystalizes in a layered orthorhombic structure with space group $Cmcm$. Analysis of its curved field-dependent Hall resistivity, using the two-band model, indicates the hole-dominated transport with a high mobility ${\mu }_h=2.38\times {10}^3{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ at low temperatures. The in-plane magnetoresistance (MR) displays significant anisotropy with field applied along the crystallographic $b$ axis. The MR with the current applied along the $c$ axis is also measured in high magnetic fields up to 51.7 T. Remarkably, it follows a power-law dependence and reaches $(9.5\times {10}^3)\%$ at 2.1 K without any signature of saturation. The de Haas–van Alphen oscillations show a small Fermi surface pocket with a nontrivial Berry phase. The Shubnikov–de Haas (SdH) oscillations are detected at low temperatures and under magnetic fields above 28.5 T. Two effective masses $m^{*}$ ($0.26m_e$ and $0.41m_e$) are extracted from the oscillatory SdH data. Our first-principles calculations unveil a topological Dirac cone in its surface states, and, in particular, the topological index indicates that ${\mathrm{TaPdTe}}_5$ is a topologically nontrivial material.

By combining angle-resolved photoemission spectroscopy, scanning tunneling microscopy, atomic force microscope based piezoresponse force microscopy and first-principles calculations, we have studied the low-energy band structure, atomic structure, and charge polarization on the surface of a topological semimetal candidate ${\mathrm{TaNiTe}}_5$. Dirac-like surface states were observed on the (010) surface by angle-resolved photoemission spectroscopy, consistent with the first-principles calculations. On the other hand, piezoresponse force microscopy reveals a switchable ferroelectriclike polarization on the same surface. We propose that the noncentrosymmetric surface relaxation observed by scanning tunneling microscopy could be the origin of the observed ferroelectriclike state in this novel material. Our findings provide a new platform with the coexistence of a ferroelectriclike surface charge distribution and novel surface states.

We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta₃Pd₃Te₁₄ containing edge-sharing PdTe₂ chains along crystallographic b axis, similar to the recently discovered superconductor Ta₄Pd₃Te₁₆. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γ_nT_c) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta₃Pd₃Te₁₄ is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta₃Pd₃Te₁₄ with a lower T_c, compared to that of Ta₄Pd₃Te₁₆, may be attributed to the lower density of states.

Because of the unique physical properties and potential applications, the exploration of quantum materials with diverse symmetry-protected topological states has attracted considerable interest in the condensed matter community in recent years. Most of the topologically nontirvial materials identified thus far have two-dimensional or three-dimensional structural characteristics, while the quasi-one-dimensional (quasi-1D) analogs are rare. Here, we report on anisotropic magnetoresistance, Hall effect, and quantum de Haas–van Alphen (dHvA) oscillations in $\mathrm{Ta}\mathrm{Pt}{\mathrm{Te}}_5$ single crystals, which possess a layered crystal structure with quasi-1D $\mathrm{Pt}{\mathrm{Te}}_2$ chains. $\mathrm{Ta}\mathrm{Pt}{\mathrm{Te}}_5$ manifests an anisotropic magnetoresistance and a nonlinear Hall effect at low temperatures. The analysis of the dHvA oscillations reveals two major oscillation frequencies (63.5 T and 95.2 T). The corresponding light effective masses and the nonzero Berry phases suggest the nontrivial band topology in $\mathrm{Ta}\mathrm{Pt}{\mathrm{Te}}_5$, which is further corroborated by the first-principles calculations. Our results suggest that $\mathrm{Ta}\mathrm{Pt}{\mathrm{Te}}_5$, in analogy with its sister compounds $\mathrm{Ta}\mathrm{Pd}{\mathrm{Te}}_5$ and $\mathrm{Ta}\mathrm{Ni}{\mathrm{Te}}_5$, is another quasi-1D material hosting topological Dirac fermions.

A Dirac nodal-line phase as a quantum state of topological materials, usually occur in three-dimensional or, at least, two-dimensional materials with sufficient symmetry operations that could protect the Dirac band crossings. Here, we report a combined theoretical and experimental study on the electronic structure of the quasi-one-dimensional ternary telluride ${\mathrm{TaPtTe}}_5$, which is corroborated as being in a robust nodal-line phase with fourfold degeneracy. Our angle-resolved photoemission spectroscopy measurements show that two pairs of linearly dispersive Dirac-like bands exist in a very large energy window, which extend from a binding energy of $\sim 0.75$ eV to across the Fermi level. The crossing points are at the boundary of Brillouin zone and form Dirac-like nodal lines. Using first-principles calculations, we demonstrate the existing of nodal surfaces on the $k_y=\pm \pi$ plane in the absence of spin-orbit coupling (SOC), which are protected by nonsymmorphic symmetry in ${\mathrm{TaPtTe}}_5$. When SOC is included, the nodal surfaces are broken into several nodal lines. By theoretical analysis, we conclude that the nodal lines along $Y\text{−}T$ and the ones connecting the $R$ points are nontrivial and protected by nonsymmorphic symmetry against SOC.