Unusual Metallic State in Superconducting A15-type La4H23

Abstract Hydride superconductors continue to fascinate the communities of condensed matter physics and material sciences because they host the promising room-temperature superconductivity. The current research has been concentrated on the new hydride superconductors with the enhancement of the superconducting transition temperature (Tc). The multiple extreme conditions (high pressure/temperature and magnetic field) will introduce new insights on the hydride superconductors. The study of transport properties under very high magnetic fields facilitates the understanding of the superconductivity in the conventional hydride superconductors. In the present work, we report experimental evidence of an unusual metal state in a newly synthesized cubic A15-type La4H23 that exhibits superconductivity with a Tc reaching 105 K at 118 GPa. A large negative magnetoresistance is observed for strong pulsed magnetic fields in the non-superconducting state below 40 K. Moreover, we construct the full magnetic phase diagram of La4H23 up to 68 T at high pressure. The present work reveals anomalous electronic structural properties of A15-La4H23 under high magnetic fields, therefore holding great importance for advancing the understanding of quantum transport behaviors in hydride superconductors.