Prediction and synthesis of Mg4Pt3H6: A superconducting complex transition metal hydride stabilized at ambient pressure

The phase behavior of the Mg-Pt-H system was explored using a combination structure prediction and HPHT experiments. A stoichiometric complex transition metal hydride with composition Mg₄Pt₃H₆ was identified using laser-heated diamond anvil cell experiments. X-ray diffraction analysis reveals that the compound possesses a body-centered cubic structural prototype, and the hydride remains stable upon quenching to ambient conditions. Mg₄Pt₃H₆ exhibits metallic electrical conductivity, which is rare among known complex metal hydrides, with formal charge described as 4[Mg]²⁺ · 3[PtH₂]²⁻. Magnetic-field and temperature-dependent electrical transport measurements indicate ambient-pressure superconductivity with T_c (50%) = 2.9 K. These findings clarify the phase behavior in the Mg–Pt–H system, highlight important synergies between computational/experimental approaches, and provide valuable insights for transition metal complex hydrides as a new class of hydrogen-rich superconductors.