Superconductivity Induced by Site-Selective Arsenic Doping in Mo5Si3

Arsenic doping in silicides has been much less studied compared with phosphorus. In this study, superconductivity is successfully induced by As doping in Mo5Si3. The superconducting transition temperature (Tc) reaches 7.7 K, which is higher than those in previously known W5Si3-type superconductors. Mo5Si2As is a type-II BCS superconductor with upper and lower critical fields of 6.65 T and 22.4 mT, respectively. In addition, As atoms are found to selectively take the 8h sites in Mo5Si2As. The emergence of superconductivity is possibly due to the shift of Fermi level as a consequence of As doping, as revealed by the specific heat measurements and first-principles calculations. Our work provides not only another example of As doping but also a practical strategy to achieve superconductivity in silicides through Fermi level engineering.