Anisotropic magnetic-field dependence of the specific heat in single-crystal-likeYBa2Cu3O7−x

Specific heat of ‘‘single-crystal-like’’ ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ is measured in magnetic field (${\mathit{B}}_{\mathit{a}}$) using adiabatic calorimetry. The field dependence of specific heat near ${\mathit{T}}_{\mathit{c}}$ for ${\mathbf{B}}_{\mathit{a}}$⊥c axis is found to be about five times lower than that for ${\mathbf{B}}_{\mathit{a}}$∥c axis. The experimental results can be understood quantitatively in terms of the Ginzburg-Landau theory of anisotropic type-II superconductors.