Scaling behavior of the specific heat of a ${\mathrm{LuBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{y}}$ single crystal near the ${\mathit{H}}_{\mathit{c}2}$ line

High-resolution specific-heat measurements have been performed on an untwinned single crystal of ${\mathrm{LuBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{y}}$ in an applied magnetic field, along the c axis, of up to 5 T. The zero-field data near the normal-superconducting transition temperature (${\mathit{T}}_{\mathit{c}}$=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.