Ambient-pressure superconductivity in covalent Au-B frameworks stabilized by electropositive metals

Extended covalent compounds that contain gold are virtually unknown because Au prefers metallic or molecular coordination. Using crystal structure search combined with first-principles calculations at high pressure, we have identified a family of ternary compounds, M₂AuB₆ (M = Na, K, Mg, Ca, and Sr), featuring Au-B covalent frameworks that satisfy a simple “push-pull” design rule: strongly electropositive cations donate charge that anchors Au in electron-deficient B₆ octahedra, thereby stabilizing Au–B σ bonds through Au dsp² hybridization. The low enthalpy phases, Na₂AuB₆ and K₂AuB₆, exhibit superconductivity, with Au-6p_x/6p_y and B-2p states contributing to Cooper pair formation, facilitated by low- and medium-frequency phonons arising from Au−B bond stretching. These pressure-induced structures and bonding configurations can be quenched to ambient pressure, demonstrating an effective approach to bypassing traditional electronegativity constraints. We propose M₂AuB₆ compounds as realistic and chemically unique platforms for exploring gold-based superconductivity and for testing electron-donor-guided materials discovery.