Two-gap superconductivity in the noncentrosymmetric La${}_3$Se${}_4$ compound

Point-contact Andreev reflection spectroscopy at low temperatures and high magnetic fields has been performed on a noncentrosymmetric La${}_3$Se${}_4$ superconductor with a critical temperature $T_c$ = 8 K. Two superconducting energy gaps ${\mathrm{\Delta }}_1$ and ${\mathrm{\Delta }}_2$ with $2{\mathrm{\Delta }}_1\mathrm{/}{k}_B{T}_c$ ~ 5.8 and $2{\mathrm{\Delta }}_2\mathrm{/}{k}_B{T}_c$ ~ 2.3, are directly observed in some of the spectra. The temperature and magnetic field effects help to resolve a two-gap structure even on the most frequent spectra where at low temperatures only a single gap is apparent, reflected in a pair of maxima around the zero bias. Two-gap superconductivity consistently with the point contact Andreev reflection spectroscopy is also supported by the heat capacity and the Hall probe magnetization measurements.