The structural and physical properties of the new titanium- and niobium-rich type-A high-entropy alloy (HEA) superconductor Nb${}_{0.34}$Ti${}_{0.33}$Zr${}_{0.14}$Ta${}_{0.11}$Hf${}_{0.08}$ (in at.%) were studied by X-ray powder diffraction, energy dispersive X-ray spectroscopy, magnetization, electrical resistivity, and specific heat measurements. In addition, electronic structure calculations were performed using two complementary methods: the Korringa–Kohn–Rostoker Coherent Potential Approximation (KKR-CPA) and the Projector Augmented Wave (PAW) within Density Functional Theory (DFT). The results obtained indicate that the alloy exhibits type II superconductivity with a critical temperature close to 7.5 K, an intermediate electron–phonon coupling, and an upper critical field of 12.2(1) T. This finding indicates that Nb${}_{0.34}$Ti${}_{0.33}$Zr${}_{0.14}$Ta${}_{0.11}$Hf${}_{0.08}$ has one of the highest upper critical fields among all known HEA superconductors.

The structural and superconducting properties of a new niobium- and titanium-rich high-entropy alloy (NbTi) $$_{\text {0.67}}$$0.67 (MoHfV) $$_{\text {0.33}}$$0.33 were determined. The alloy was synthesized by arc melting and its physical properties were characterized by means of X-ray powder diffraction, energy dispersive X-ray spectroscopy, magnetization, electrical resistivity and specific heat measurements. Experimental data revealed that the (NbTi) $$_{\text {0.67}}$$0.67 (MoHfV) $$_{\text {0.33}}$$0.33 crystalizes in body-centered cubic structure and exhibits type-II superconductivity below about 5 K. In addition, electronic structure calculations were performed using the Density Functional Theory (DFT) method. Their results suggest that in case of HEAs, the influence of the local atomic configuration on their electronic structure in the energy region close to E $$_{\mathrm {\text {F}}}$$F is rather small or even negligible.

High-entropy alloys (HEAs) with body-centred cubic (bcc) structures possess one of the highest critical parameters among HEA superconductors, making them one of the most promising candidates for practical applications in their field. This review systematically compares experimental data and theoretical predictions from density functional theory (DFT) for superconducting bcc HEAs, focusing on critical parameters such as the superconducting critical temperature, the Debye temperature, and the electron-phonon coupling constant. Although DFT provides valuable information on electronic structures, lattice dynamics, and thermodynamic stability, significant discrepancies persist between the computed and measured parameters. Possible reasons for this are discussed.

Superconducting alloy containing terbium (Tb) and its reference without the lanthanide were synthesized. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific heat, and magnetic measurements were used to investigate their structural and physical properties. Both alloys crystallized in body-centered cubic structure, and the presence of small amounts of Tb and Tb₂O₃ phases was detected. The critical temperature $T_{\mathrm{c}}$ of alloys was in the 4.6–5.2 K range, and the upper critical field ${\mu }_0{H}_{\mathrm{c}2}$ was 6.1–6.8 T. The comparison with the reference determined the effect of Tb on the alloy’s critical parameters and phase stability connected to the high-entropy alloys’ core effects. Overall, Tb addition did not have a beneficial effect on the superconducting properties of this alloy.