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, the discovery of superconductivity is reported with an onset transition temperature up to 14.2 K in a Mn-based material MnB₄, which is the highest value among the stoichiometric Mn-based superconductors. By applying high pressure, the continuous suppression of a weak semiconducting behavior and the occurrence of superconductivity after ≈30 GPa are found. With further increasing pressure, the superconducting transition temperature (T_c) is gradually enhanced and reaches the maximum onset transition value of ≈14.2 K at 150 GPa. 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 in a certain pressure region as confirmed by the theoretical calculation. The findings show a promising way to explore high T_c superconductivity by combining the 3d-transition metal magnetic elements and light elements.