Mo3ReRuC: A Noncentrosymmetric Superconductor Formed in the MoReRu–Mo2C System

A quaternary compound with the composition Mo3ReRuC is obtained in a previously unexplored MoReRu–Mo2C system. According to X-ray structural analysis, Mo3ReRuC crystallizes in the noncentrosymmetric space group P4132 [cubic β-Mn-type structure, a = 6.8107(1) Å]. Below 7.7 K, Mo3ReRuC becomes a bulk type-II superconductor with an upper critical field close to the Pauli paramagnetic limit. The specific heat data give a large normalized jump ΔC p/γT c = 2.3 at T c, which points to a strongly coupled superconducting state. First-principles calculations show that its electronic states at the Fermi level are mainly contributed by Mo, Re, and Ru atoms and strongly increased by the spin–orbit coupling. Our finding suggests that the intermediate phase between alloys and carbides may be a good place to look for β-Mn-type noncentrosymmetric superconductors.