Anisotropic specific-heat behavior under a magnetic field of a YBa sub 2 Cu sub 3 O sub 7 single crystal

Specific-heat experiments have been performed on single-crystal ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ under magnetic fields up to 6 T applied parallel and normal to the (ab) planes. The curves show a weak influence of the field parallel to (ab) on the ${\mathit{C}}_{\mathit{p}}$ anomaly, by comparison with the smearing effect observed when the field is normal to the (ab) planes. These results are consistent with the recently published magnetic data, which allow us to calculate the anisotropy factor of the ${\mathit{C}}_{\mathit{p}}$ discontinuity and the entropy changes under a field.