Pressure Induced Clathrate Hydrogen-Rich Superconductors KH 20 and KH 30 .

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 20 and KH 30 , hosting high superconducting transition temperatures ( T c ) 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- T c . 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 36 cages. These results offer key insights into the stability and potential high- T c superconductivity of compressed extreme superhydrides and will further stimulate related research.