Ambient-pressure high-temperature superconductivity in stoichiometric hydrogen-free covalent compound BSiC2

High superconducting critical temperature ( T c ) of 73.6 K at ambient pressure is predicted in BSiC 2 by means of the first-principles electron–phonon calculations. Without the need for doping or pressurization, the stoichiometric BSiC 2 exhibits strong electron–phonon coupling (EPC) and highest T c among BCS-superconductors at ambient pressure. Also, it is hydrogen-free that makes easier the sample growth. The dramatic softening of the E 2 g mode is the main account for the strong EPC. In addition, we find that BC 3 , derived from the replacement of Si in BSiC 2 by another C, is also superconducting with a high T c ∼ 40 K. Our work indicates that these materials form a new family of high- T c BCS-superconductors at ambient pressure.