THE NEGATIVE THERMOPOWER AND THE SUPPRESSION OF SUPERCONDUCTIVITY IN ND-DOPED LA2-XBAXCUO4 WITH X AROUND 1 8/

In the study of La2-x-yNdyBaxCuO4 we found that the structural phase t ransition (OMT-TLT) is observed in a wider range of x (0.10 less than or equal to x less than or equal to 0.200) than the suppression of sup erconductivity is evident (0.120 less than or equal to x less than or equal to 0.140). A minimum in resistivity and an unusual decrease of t he thermopower occur at the same temperature for x around 1/8. Below 3 0K the thermopower becomes negative associated with the suppression of superconductivity. This means that the suppression of superconductivi ty is directly caused by a sort of instability in the electronic state s.