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 untwinned 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-superconducting transition temperature (Tc=92.5 K) display a very large and sharp specific-heat anomaly. Among various models for scaling the magnetic field and temperature-dependent specific-heat data, a model which incorporates the two-dimensional nature of this transition provides the best description of our data. A narrow region of crossover to three-dimensional behavior is also observed.