Pressure dependence of superconducting-transition temperature of YbGa1.1Si0.9

Pressure dependence of the superconducting transition temperature Tc has been investigated in YbGa1.1Si0.9, which is the AlB2-type layered superconductor with Tc = 2.4 K. The electrical resistivity measurements were carried out under hydrostatic pressure up to 2.5 GPa using a piston-cylinder type pressure cell. With increasing pressure, the Tc of YbGa1.1Si0.9 decreases from 2.4 K to 1.1 K at 2.5 GPa with a pressure derivative of Tc, dTc/dP, of - 0.78 K/GPa. This negative pressure derivative of Tc is similar to the other superconducting AlB2-type silicides. The relative pressure derivative of Tc, dlnTc/dP, for YbGa1.1Si0.9 is - 0.33 GPa-1, which is about ten times larger than those for other layered superconductors.