Effect of pressure on the superconductivity of Rb0.19WO3

We have performed electrical resistivity measurements under pressures up to 20 GPa between 1 and 300 K on monocrystalline hexagonal Rb0.19WO3. For pressures lower than ∼5 GPa, we observe a decrease of the metallic-like resistivity at room temperature as well as a small decrease of Tc. At this pressure, the resistivity starts to increase slowly up to 10 GPa accompanied by a sharper decrease of Tc.The resistivity curves above 10 GPa denote an activated behaviour and a Tc lower than 3 K indicating that there is a phase transition that takes place gradually between 5 and 10 GPa. We interpret our measurements as the result of structural transformations under high pressure.