Located at crystal voids, interstitial anion electrons (IAEs) have diverse topologies, which may be tuned to achieve different properties. Elucidating the role of IAEs in electron-phonon coupling (EPC), and using it to design electride superconductors, leads to the current prediction of superconducting ${\mathrm{Li}}_8\mathrm{Au}$ at high pressure. We suggest that the occurence of high-temperature superconductivity in electrides requires high-symmetry structures with hydrogenlike cages, an electron acceptor element to balance charges, and isolated IAEs coupled with medium-frequency vibrations. The uniquely designed ${\mathrm{Li}}_8\mathrm{Au}$ electride has a NaCl-type ($B1$) lattice, with atomic Au and cubic ${\mathrm{Li}}_8$ cages as bases. Isolated IAEs are formed at the cage centers, with extra charges taken up by Au. These octahedrally coordinated IAEs have a $p$-orbital-like attribute and are strongly coupled with atomic vibrations in the ${\mathrm{Li}}_8$ cages. The strong EPC in ${\mathrm{Li}}_8\mathrm{Au}$ results in a calculated $T_c$ of 73.1 K at 250 GPa, which is the highest $T_c$ reported to date for all the electrides. A slight substitutional Pt doping can enhance the $T_c$ of ${\mathrm{Li}}_8\mathrm{Au}$ to exceed liquid nitrogen temperature.

• Received 7 October 2022
• Revised 19 December 2022
• Accepted 27 February 2023

DOI:https://doi.org/10.1103/PhysRevB.107.L100501