High pressure studies on YNi2B2C and LuNi2B2C: ADXRD, thermoelectric power, resistivity, and electronic structure

The electronic and structural behaviour of YNi2B2C and LuNi2B2C at high pre ssures were investigated by electrical resistivity, thermoelectric power (T EP), and angle dispersive X-ray diffraction measurements and by electronic band structure calculations. The pressure variation of TEP shows a peak aro und 2 GPa in YNi2B2C. However, the X ray powder diffraction does not show a ny structural transition up to 16.4 GPa. The equation of state of YNi2B2C y ielded a relatively high bulk modulus of 200 GPa. The observed peak in TEP and the pressure variation of the superconducting transition temperature ca n be correlated with different components of the electronic density of stat es. The universal equation of state shows deviation from linearity around 1 .5 GPa pressure and correlates well with the TEP peak. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.