de Haas-van Alphen effect of the heavy-fermion superconductor URu2Si2

We have measured the de Haas-van Alphen (dHvA) effect of URu2Si2. One kind of the dHvA branch, which corresponds to an almost spherical Fermi surface, has been detected both in the normal and super-conducting mixed states. Th e dHvA frequency in the mixed state is unchanged from the normal state. The cyclotron effective mass is clearly found to decrease with decreasing the magnetic field below H-c2 and the corresponding Dingle temperature increase s with decreasing the held. (C) 1999 Elsevier Science B.V. All rights reser ved.