Pressure Induced Clathrate Hydrogen-Rich Superconductors KH and KH.

Hydrogen-rich compounds have long been considered as one of the hotspot materials for achieving room-temperature superconductivity. We systematically investigate the high-pressure phase diagram of the K-H system and identified two unreported clathrate extreme superhydrides KH and KH, hosting high superconducting transition temperatures () of 283 and 243 K at 500 GPa, respectively. The extremely high hydrogen content significantly increases H-derived electronic density of states at the Fermi level, constituting the main contributor to participate in electron-phonon coupling thus producing high-. The large electron localizations in the interstitial region of the metal lattice under high pressure effectively assist the dissociation of hydrogen molecular units, forming unique H cages. These results offer key insights into the stability and potential high- superconductivity of compressed extreme superhydrides and will further stimulate related research.