SCALING BEHAVIOR OF THE SPECIFIC-HEAT OF A LUBA2CU3O7-Y SINGLE-CRYSTAL NEAR THE HC2 LINE

High-resolution specific-heat measurements have been performed on an u ntwinned single crystal of LuBa2Cu3O7-y in an applied magnetic field, along the c axis, of up to 5 T. The zero-field data near the normal-su perconducting transition temperature (T(c) = 92.5 K) display a very la rge and sharp specific-heat anomaly. Among various models for scaling the magnetic field and temperature-dependent specific-heat data, a mod el which incorporates the two-dimensional nature of this transition pr ovides the best description of our data. A narrow region of crossover to three-dimensional behavior is also observed.