Robust properties of the superconducting ferromagnet UCoGe

The angular dependent magnetoresistance of the superconducting ferromagnet UCoGe is studied in detail at 40 mK to fields of 18 T in a single crystal sample with a low residual resistivity ratio [R(300 K)/R(1 K)=RRR=5]. A ferro-to-ferrimagnetic transition near 9 T that depends only on the field component along the uniaxial magnetic c axis is observed in both transport and susceptibility. Reverse hysteresis in the magnetoresistance in the critical field region indicates a coupling of the superconductivity to the magnetization for fields aligned closely to the ab plane. These results corroborate and advance previous findings on higher residual resistivity ratio samples.