Epitaxial thin films of the heavy fermion superconductor UNi2Al3 with T max c = 0.98K were investigated. The transition temperature Tc depends on the current direction which can be related to superconducting gaps opening at different temperatures. Also the influence of the magnetic ordering at TN ≃ 5K on R(T ) is strongly anisotropic indicating different coupling between the magnetic moments and itinerant charge carriers on the multi-sheeted Fermi surface . The upper critical field Hc2(T ) suggests an unconventional spin-singlet superconducting state.PACS numbers: 74.70. Tx, 74.25.Fy, 74.78.Db Recently a clear progress concerning the superconductivity of the heavy fermion compound UPd 2 Al 3 was reported. Due to combined experimental investigations based on tunneling spectroscopy on planar thin film junctions [1] and inelastic neutron scattering [2, 3, 4] an unconventional mechanism of superconductivity was identified. There is compelling evidence that the Cooper pair formation in this compound is caused by the exchange of magnetic excitations. However, the question if these excitation are spin fluctuations [5] or magnetic excitons [4,6] is not finally answered. In this framework the investigation of the compound UNi 2 Al 3 , which is isostructural to UPd 2 Al 3 , is of great interest. Whereas UPd 2 Al 3 shows a simple antiferromagnetic structure with relatively large ordered magnetic moments of µ ord ≃ 0.85µ B the compound UNi 2 Al 3 is an incommensurately ordered antiferromagnet [7] with smaller ordered moment µ ord ≃ 0.24µ B [8]. In contrast to UPd 2 Al 3 , for UNi 2 Al 3 there is evidence for a spin-triplet superconducting state [9].

No abstract

No abstract

No abstract

No abstract