Pressure-stabilized Li₂K electride with superconducting behavior

Compression of alkali elements makes them depart gradually from the s-band metals, leading to exotic physical and chemical properties. Here, we report the chemical reaction Li + K → Li₂K under high pressure by using a swarm intelligence structure searching methodology combined with first-principles calculations. Li₂K has three stable/metastable structures and undergoes the pressure-induced phase transitions C2/m → Fddd → I4/mmm at 226 GPa and 291 GPa, respectively. Notably, this system features significant s → p and s → d charge transfers as well as a topologically zero-dimensional electride character. Under 300 GPa, Li₂K manifests exceptional superconductivity with a critical temperature (T_c) of 39 K, attributed to the orbital hybridization between Li p states and interstitial quasi-atom-derived s electrons, and their robust coupling with Li and K phonon modes. This work serves as a crucial reference for exploring novel superconducting electrides.