ANOMALOUS PRESSURE-TEMPERATURE PHASE-DIAGRAM OF THE MOLECULAR CONDUCTOR, (DI-DCNQI)(2)CU (DI-DCNQI=2,5-DIIODO-N,N'-DICYANOQUINONEDIIMINE)

We report the temperature-dependent resistivity under pressure up to 2 2 kbar and the crystal and electronic band structures for the molecula r conductor (DI-DCNQI)(2)Cu. In the (DCNQI)(2)Cu system, the applicati on of pressure induces the metal-insulator (M-I) transition. (DI-DCNTQ I)(2)Cu shows the highest critical pressure (15.3 kbar). In contrast t o previously reported (DCNQI)(2)Cu systems, however, this system turns into metallic state again above 20 kbar. This anomalous phenomenon is discussed in terms of an enhancement of the intercolumn LUMO...LUMO i nteraction.