Unusual upper critical field of the ferromagnetic superconductor UCoGe

We report upper critical field B-c2(T) measurements on a single-crystalline sample of the ferromagnetic superconductor UCoGe. B-c2(0) obtained for fields applied along the orthorhombic axes exceeds the Pauli limit for B parallel to a,b and shows a strong anisotropy B-c2(a)similar or equal to B-c2(b)> B-c2(c). This provides evidence for an equal-spin pairing state and a superconducting gap function of axial symmetry with point nodes along the c axis, which is also the direction of the uniaxial ferromagnetic moment m(0)=0.07 mu(B). An unusual curvature or kink is observed in the temperature variation of B-c2, which possibly indicates UCoGe is a two-band ferromagnetic superconductor.