Superconductivity in U-Nb alloys with γ-U phase and ferromagnetism of their hydrides

U-Nb alloys with Nb concentration in the range of 0-20 at. % were prepared using a splat-cooling technique with a cooling rate of 106 K/s. Structure analysis by X-ray diffraction revealed a stabilization of the γ-U phase in alloys with ≥15 at. % Nb concentration. The investigated materials become superconducting below Tc = 1.90 K and the critical field μ0Hc2(0) can reach 5.4 T. The hydrogen absorption in U-15 at.% Nb (U0.85Nb0.15) at high hydrogen pressures exceeding 4 bar leads to a formation of the hydride (UH3)0.85Nb0.15. It is a ferromagnet with TC ≈ 195 K and a magnetic moment of 0.80 μB/U.