de Haas-van Alphen effect in the superconducting state of YNi2B2C

To examine the Fermi surfaces of the recently discovered quaternery compounds RENi₂B₂C measurements of the de Haas-van Alphen (dHvA) effect were made on YNi₂B₂C single crystals in magnetic fields up to 12 T. ForBc we observe two dHvA frequenciesF ₁=0.499 kT andF ₂=6.933 kT which corresponds to approximately 1,5% and 21% of the Brillouin zone cross section area. Both frequencies could be observed deep in the vortex state of the type-II superconductor, the lower dHvA frequency down to 2 T corresponding to roughly 1/5 of the upper critical fieldB _c2 which was found to be 10.6 T in resistivity measurements. The field dependent quasiparticle damping in the superconducting state is very weak, since the amplitude of the dHvA oscillations seems to be unaffected by the phase transition atB _c2.