Superconductivity and high hardness in metal-rich carbides MoRe2C and WRe2C

We report the results of structural, mechanical and physical property studies on two new carbides MoRe2C and WRe2C, which were not identified in previous Mo-Re-C and W-Re-C phase diagrams. These ternary phases adopt a face-centered cubic structure at ambient pressure likely with a disordered atomic arrangement. Due to the covalent bonds between transition metal and carbon atoms, MoRe2C and WRe2C exhibit high hardness values of 15.3 GPa and 13.7 GPa, respectively. Furthermore, these carbides are discovered to be bulk superconductors with very similar Tc values about 4.50 K. The analysis of their specific-heat jumps points to a weakly coupled, fully gapped superconducting state. The electron-phonon coupling constant, upper critical field and coherence length are estimated to be 0.56, 5.3 T and 7.9 nm for MoRe2C, and 0.57, 6.3 T, 7.2 nm for WRe2C. Our results suggest that transition-metal-rich carbides provide a platform to study the link between configurational disorder, high hardness and superconductivity. •MoRe2C and WRe2C with a face-centered cubic structure are synthesized.•The disordered atomic distribution results in a medium configurational entropy.•MoRe2C and WRe2C have high hardnesses of 15.3 GPa and 13.7 GPa, respectively.•Both carbides are weakly coupled, fully gapped superconductors below 4.5 K.