Pressure Induced Clathrate Hydrogen-Rich Superconductors KH₂₀ and KH₃₀

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 KH₂₀ and KH₃₀, 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 H₃₆ 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.