Superconductivity in Mo${}_4$Ga${}_{20}$As with Endohedral Gallium Clusters

Abstract

We report the discovery and detailed investigation of superconductivity in Mo${}_4$Ga${}_{20}$As. Mo${}_4$Ga${}_{20}$As crystallizes in the space group of $I4/m$ (No. 87), with lattice parameters $a$ = 12.86352 Ã and $c$ = 5.30031 Ã . The resistivity, magnetization, and specific heat data reveal Mo${}_4$Ga${}_{20}$As to be a type-II superconductor with $T_c$ = 5.6 K. The upper and lower critical fields are estimated to be 2.78 T and 22.0 mT, respectively. In addition, electron-phonon coupling in Mo${}_4$Ga${}_{20}$As is possibly stronger than the BCS weak-coupling limit. First-principles calculations suggest the Fermi level being dominated by the Mo-4$d$ and Ga-4$p$ orbitals.