Doping-induced superconductivity in the topological semimetal Mo₅Si₃

Chemical doping of topological materials may provide a possible route for realizing topological superconductivity. However, all such cases known so far are based on chalcogenides. Here we report the discovery of superconductivity induced by Re doping in the topological semimetal Mo₅Si₃ with a tetragonal structure. Partial substitution of Re for Mo in Mo₅-_xRe_xSi₃ results in an anisotropic shrinkage of the unit cell up to the solubility limit of approximately x = 2. Over a wide doping range (0.5 ≤ x ≤ 2), these silicides are found to be weakly coupled superconductors with a fully isotropic gap. T_c increases monotonically with x from 1.67 to 5.78 K, the latter of which is the highest among superconductors of the same structural type. This trend in T_c correlates well with the variation of the number of valence electrons and is mainly ascribed to the enhancement of electron-phonon coupling. In addition, band structure calculations reveal that superconducting Mo₅-_xRe_xSi₃ exhibits nontrivial band topology characterized by Z₂ invariants (1;000) or (1;111) depending on the Re doping level. Our results suggest that transition metal silicides are a fertile ground for the exploration of candidate topological superconductors.