We present very low-temperature scanning tunneling microscopy (STM) experiments on single-crystalline samples of the superconductor $\beta -{\mathrm{Bi}}_2\mathrm{Pd}$. We find a single superconducting gap from the zero-field tunneling conductance. However, the magnetic field dependence of the intervortex tunneling conductance is higher than the one expected in a single-gap superconductor. Such an increase in the intervortex tunneling conductance has been found in superconductors with multiple superconducting gaps. We also find that the hexagonal vortex lattice is locked to the square atomic lattice as expected in crystalline superconductors with anisotropic Fermi surfaces. Moreover, we compare the upper critical field $H_{c2}\left(T\right)$ obtained in our sample with previous measurements and find that $H_{c2}\left(T\right)$ does not increase by reducing the mean free path. We fit $H_{c2}\left(T\right)$ and show that multiband Fermi surface is needed to explain the observed behavior. We propose that $\beta -{\mathrm{Bi}}_2\mathrm{Pd}$ is a single-gap multiband superconductor. We anticipate that single-gap superconductivity might often occur in compounds with anisotropic multiband Fermi surfaces.

SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe_0.98(2) and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 μV K⁻¹ at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m⁻¹ K⁻¹ around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material.

Thermoelectric materials may contribute in the near future as new alternative sources of sustainable energy. Unprecedented thermoelectric properties in p-type SnSe single crystals have been recently reported, accompanied by extremely low thermal conductivity in polycrystalline samples. In order to enhance thermoelectric efficiency through proper tuning of this material we report a full structural characterization and evaluation of the thermoelectric properties of novel Ge-doped SnSe prepared by a straightforward arc-melting method, which yields nanostructured polycrystalline samples. Ge does not dope the system in the sense of donating carriers, yet the electrical properties show a semiconductor behavior with resistivity values higher than that of the parent compound, as a consequence of nanostructuration, whereas the Seebeck coefficient is higher and thermal conductivity lower, favorable to a better ZT figure of merit.