Fermi surface and de Haas-van Alphen oscillation in both the normal and superconducting mixed states of UPd2Al3

The dHvA oscillation was observed clearly in both the normal and superconducting mixed states for UPd2Al3 with the hexagonal structure. Eight kinds of dHvA branches were detected, which are well explained by the results of band calculations based on a fully-relativistic spin-polarized LAPW method. An inner orbit of a hand 41-hole Fermi surface; named zeta, has the largest dHvA frequency of 9.45x10(7) Oe and cyclotron mass of 65 m(0), reflecting a large electronic specific heat coefficient of 145 mJ/K-2.mol. Branch alpha of a hand 40-hole Fermi surface was observed in both the normal and superconducting mixed states, where the dHvA frequency does not change in magnitude between the normal and mixed states. The cyclotron effective mass of branch alpha is, however, found to be reduced and the corresponding Dingle temperature or scattering rate of the conduction electron increases with decreasing the field in the mixed state. An anisotropic energy gap with a line node for UPd2Al3 is discussed from the angular dependence of the dHvA amplitude in the mixed state.