Record Superconductivity in a Kagome Calcium Boride at High Pressure

Exotic stoichiometric light-element compounds stabilized by high pressure deliver a plentiful playground in the search for high-temperature superconductors. The experimental discovery of new superconducting phases in this system has been greatly hurdled owing to their complex crystal structures and rich physical phenomena despite numerous theoretical predictions. Here we demonstrate the high-pressure synthesis of a kagome superconductor <i>P</i>6/<i>mmm</i> CaB₃ with <i>T</i>_c ∼ 22 K, higher than any of the already known kagome superconductors. Based on theoretical calculations, the superconductivity in <i>P</i>6/<i>mmm</i> CaB₃ is predominantly driven by the coupling of the vibrations between the B kagome lattice and the <i>p</i>-orbital electrons of B. This research elucidates an unprecedented kagome lattice in the Ca-B system, providing profound insights for the exploration of light-element superconductors.