Superconductivity and magnetism in noncentrosymmetric RhGe

RhGe synthesized at high pressure crystallizes in the noncentrosymmetric B20 cubic structure. Measurements of electrical resistivity and magnetization demonstrate a superconducting state below Tc ∼ 4.3 K and weak ferromagnetism below Tm ∼ 140 K. Specific heat data confirm the bulk nature of superconductivity in this ferromagnetic superconductor. Point contact spectra in the superconducting state exhibit the complex Andreev reflection signal which may indicate a mixed singlet-triplet order parameter. The superconducting region forms a dome on the P-T diagram with a maximum of Tc near 4 GPa. It was also found that the superconductivity of RhGe4 is suppressed at high pressure in contrast with RhGe. Ab initio simulations suggest that the observed weak magnetization emerges from the pronounced toroidal-like spin polarization with magnetic quadrupole and toroidal moments located at Rh and Ge sites.