Superconductivity and the low-temperature orthorhombic to tetragonal phase transition in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Ba}}_{\mathit{x}}$${\mathrm{CuO}}_4$

The relationship between the low temperature orthorhombic-tetragonal (OT) phase transition in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ba}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ and the suppression of the superconducting state in samples with x=0.125 has been investigated. Using high resolution synchrotron x-ray diffraction we show that the phase composition of a superconducting x=0.15 sample varies with temperature identically to an x=0.125 sample. This shows that the tetragonal structure does support bulk superconductivity in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ba}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ and the electronic transition which suppresses superconductivity at x=0.125 is distinct from the OT structural transition.