  High-temperature superconductivity has been observed in binary hydrides such
as LaH10 at pressures above 150 GPa. Hydrogen cage structures have been
identified as a common motif beneficial for high critical temperatures Tc.
Efforts are now focused on finding hydride high-temperature superconductors at
lower pressures. We present evidence for high-temperature superconductivity in
binary La4H23 with A15-type structure featuring hydrogen cages at a pressure of
P = 95 GPa. We synthesise La4H23 from a lanthanum film capped with a palladium
catalyst promoting the dissociation of hydrogen. In resistance measurements, we
observe superconductivity with a transition temperature Tc = 90 K. In X-ray
diffraction on the same sample, we identify the A15-type cubic body centred
structure of the lanthanum sublattice. From comparison with earlier XRD and
structure prediction studies, we identify this phase with La4H23. Our study
reinforces the concept of hydrogen cages for high-temperature
superconductivity.
