DE HAAS-VAN-ALPHEN EFFECT IN THE SUPERCONDUCTING STATE OF YNI2B2C

To examine the Fermi surfaces of the recently discovered quaternery compounds RENi(2)B(2)C measurements of the de Haas-van Alphen (dHvA) effect were made on YNi(2)B(2)C single crystals in magnetic fields up to 12 T. For B parallel to e we observe two dHvA frequencies F(1) = 0.499 kT and F(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 field B(c)2 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 at B(c)2.