The anomaly of the specific heat of La2‐xSrxCuO4+δ near Tc

The specific heat of three polycristalline samples of La 2−x Sr x CuO 4+δ (x = 0.15, 0.15, 0.16) near T c was measured with a resolution better than 0.1%. The anomaly at T c is analysed for fluctuations for the first time. It is well described by a superposition of a mean field step and a contribution due to gaussian fluctuations. By a fit of a Lawrence-Doniach type of model to the specific heat near T c we estimate ΔC MF and the anisotropic coherence lengths ξ ∥ and ξ ⊥ of the superconductor