${\mathrm{TbBaCo}}_2{\mathrm{O}}_{5.48}$ has been studied by high-pressure synchrotron x-ray diffraction together with resistivity measurements as a function of temperature and pressure. It was found that under pressure a structural phase transition takes place corroborating with a sluggish insulator-to-metal transition. An onset of the metallic state was deduced from a gradual drop of resistivity at the range 3–10 GPa culminating into the change in sign of $dR/dT$, from negative to positive, at $P\ge 10\mathrm{GPa}$; at the same pressure range there is a change of lattice strain components calculated from the unit cell dimensions. The changes in structural and transport properties are very similar to those found on heating at ambient pressure implying a common mechanism.

• Received 4 May 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.125501