The specific-heat jump at a normal-superconducting phase transition in an anisotropic superconductor with nonmagnetic impurities is calculated within a weak-coupling mean-field approximation. It is shown that its dependence on the impurity concentration is remarkably different for ${\mathrm{d}}_{{\mathrm{x}}^2\mathrm{-}{\mathrm{y}}^2}$-wave and (${\mathrm{d}}_{{\mathrm{x}}^2\mathrm{-}{\mathrm{y}}^2}$+s)-wave states. This effect may be used as a test for the presence of an s-wave admixture in the cuprates.

• Received 27 September 1996

DOI:https://doi.org/10.1103/PhysRevB.55.11778