Superconductivity in metal borocarbide MBC5 and M2BC11 compounds.

The superconductivity of MBC10 and M2BC11 ternary compounds, with M being the group 1-3 metal elements, are systematically studied by first principles calculations. Superconductivity with critical temperature Tc below 10K is predicted for MBC10 compounds when M are alkali earth or La atoms. For M2BC11 compounds, superconductivity with Tc below 5 K is predicted for M = Na, K, and Cs, while higher Tc is predicted for M =Mg and Ca. Particularly, the Mg₂BC₁₁ exhibits an exceptionally high Tc of 43.9 K. The results obtained by our first-principles calculations enrich our knowledge in the structure and superconductivity of metal borocarbide ternary compounds and provide useful guidance for further experimental synthesis and discovery.