DHvA oscillation in the anisotropic superconductors of UPd2Al3 and URu2Si2

UPd2Al3 and URu2Si2 are considered to be non-s-wave superconductors with an anisotropic energy gap from the NMR and specific heat measurements. We hav e succeeded in observing clearly the dHvA oscillation in both the normal an d superconducting mixed states. The cyclotron mass is found to be reduced a nd the Dingle temperature increases in the mixed state. An anisotropic ener gy gap with a line node for UPd2Al3 and URu2Si2 was discussed from the angu lar dependence of the dHvA amplitude in the mixed state. (C) 2000 Elsevier Science B.V. All rights reserved.