Anomalous Structural Behavior of the Superconducting Compound ${\mathrm{La}}_{1.85}$${\mathrm{Ba}}_{0.15}$Cu${\mathrm{O}}_4$

High-resolution neutron powder diffraction experiments on the superconducting compound ${\mathrm{La}}_{1.85}$ ${\mathrm{Ba}}_{0.15}$Cu${\mathrm{O}}_4$ have revealed the presence of a tetragonal-to-orthorhombic phase transition at 180 K, together with subtle, anomalous structural instabilities at lower temperatures. These experiments demonstrate a correlation between the structural anomalies and changes in the electrical resistivity.