We predict superconductivity for the carbon--boron clathrate SrB₃C₃ with T₂=27--430. 28em{0ex}K for Coulomb pseudopotential (μ ∗) values between 0. 17 and 0. 10 using first-principles calculations with conventional electron--phonon coupling. Electrical transport measurements, facilitated by an in situ experimental design compatible with extreme synthesis conditions (>30000. 28em{0ex}K at 50 GPa), show nonhysteretic resistivity drops that track the calculated magnitude and pressure dependence of superconductivity for μ ∗ ≈ 0. 15, and transport measurements collected under applied magnetic fields indicate superconductivity with an onset T₂ of approximately 20 K at 40 GPa. Carbon-based clathrates thus represent a class of superconductors similar to other covalent metals like MgB₂ and doped fullerenes. Carbon clathrates share structures similar to superconducting superhydrides with wide potential for tunable properties, and covalent C--B bonds allow metastable persistence at ambient conditions.
Zhu et al. (Thu,) studied this question.