D-WAVE SCALING RELATIONS IN THE MIXED-STATE SPECIFIC-HEAT OF YBA2CU3O7

The low temperature specific heat C(T,B) of an YBa2Cu3O7.00 single cry stal is measured from 1.2 to 10 K in magnetic fields up to 14 T. The a nisotropic component C-aniso(T,B) drop C(T, B parallel to c) - C(T, B perpendicular to c), a pure vortex quantity obtained directly from exp eriment, is found to obey a scaling relation predicted recently for su perconductors with line nodes in the gap. Our experimental field and t emperature range correspond to a crossover region, where the limit C-a niso(T,B) alpha TB1/2 does not strictly apply. The variation of the en tropy caused by the magnetic field at low T is thermodynamically compa tible with measurements near T-c.