Fig. 2.

T–P phase diagram of (Li_1−xFe_x)OHFe_1−ySe with an ambient-pressure T_c = 40 K. a Pressure dependence of the superconducting transition temperatures T_cs and a contour color plot of the normal-state resistivity exponent α up to 12.5 GPa. The values of T_c^onset, T_c^zero, and T_c^χ were determined from the high-pressure resistivity and AC magnetic susceptibility. The temperature dependence of α are extracted from dln(ρ − ρ₀)/dlnT for each pressure. b Pressure dependences of the Hall coefficient R_H and the electron density n_e up to 8 GPa extracted from the transverse resistivity ρ_xy. Pressure dependence of the resistivity coefficient A in the plot of ρ ~ AT² below 5 GPa. A double-domed T_c(P) accompanied with distinct normal-state properties for each superconducting phase is clearly observed. The reemergence of the SC-II phase with higher T_c is accompanied with a dramatic enhancement of the carrier density n_e