Superconductivity up to 14.2 K in MnB₄ under pressure

The discovery of superconductivity in 3d-transition metal compounds with strong magnetism is interesting but rare. Especially for Mn-based compounds, there exist only very limited materials that show superconductivity. Here, we report the discovery of superconductivity up to 14.2 K in a Mn-based material MnB₄. By applying high pressures, we found the continuous suppression of a weak insulating behavior and the occurrence of superconductivity after about 30 GPa. With further increasing pressure, Tc is gradually enhanced and reaches the maximum value of about 14.2 K at 150 GPa with a Fermi-Liquid behavior in the normal states. The synchrotron X-ray diffraction data reveal the unchanged monoclinic (S.G: P2₁/c) symmetry but an unusual crossover of the lattice parameters b and c. Theoretical calculations based on the electron-phonon coupling picture reveal a very low Tc (less than 1 K), manifesting an exotic pairing mechanism beyond the Bardeen-Cooper-Schrieffer (BCS) theory. Our findings show a promising way to explore high Tc superconductivity by combining the 3d-transition metal magnetic elements and light elements.