EFFECTS OF PRESSURE ON THE ELECTRICAL RESISTIVITIES OF PRBA2CU4O8 ANDPR2BA4CU7O15-DELTA

We have investigated the effects of pressure on the electrical resisti vities of PrBa2Cu4O8 (Pr124) and Pr2Ba4Cu7O15-delta (Pr247). The tempe rature coefficient of the resistivity is positive below 150-190 K (T-m ) while that above T-m is negative for both systems. We found that the resistivity below T-m is insensitive to pressure in the pressure rang e 0-1 GPa and by contrast the resistivity above T-m remarkably increas es with increasing pressure. At higher pressures the resistivity below T-m is also affected by pressure. We attribute the positive temperatu re coefficient of the resistivity below T-m to the metallic conduction along the double chains and the negative one above T-m to the semicon ducting conduction through the CuO2 planes.