ELECTRONIC TRANSPORT AND SPECIFIC-HEAT OF CA-DOPED YBA2CU3OX-SINGLE CRYSTALS

Measurements of the anisotropic electrical resistivity, the Hall Effec t, and the specific heat anomaly at T-c of Ca-doped YBa2Cu2Ox single c rystals of various Ca and O contents are presented. The transport prop erties are discussed in terms of charge and spin separated quasipartic les and confirm that by doping Ca onto Y sites the hole concentration, n(h), can be extended beyond the value achieved with O-doping alone a t x=7.0. The jump in the specific heat at T-c which increases monotono usly with x up to x=7.0 in Ca-free crystals displays a maximum in high ly oxygenated Ca-doped crystals. This maximum, however, is displaced f rom the T-c(n(h)) maximum to higher values of n(h), consistent with th e model of induced superconductivity in the CuO chains.