Anomalous behavior of the structural and thermodynamic characteristics of the ceramic La1.8Sr0.2CuO4 on going over into the superconducting state

X-ray investigations of the ceramic La1.8Sr0.2CuO4 have been carried out in the temperature range 5–293 °K. A lowering of the lattice symmetry from tetragonal to orthorhombic was established for T<200 °K. Singularities in the temperature dependence of the lattice parameters and molar volume and anomalies in the thermal expansion were found in the region of the superconducting transition, correlated in temperature with anomalies in the specific heat.