HIGHLY CONDUCTING 1 1 RADICAL-CATION SALTS - (DMTSA)X WITH X=NO3 AND BF4/

(DMTSA)NO3 and -BF4 show high conductivity at room temperature, in spi te of fully ionic salt of 1:1 stoichiometry with uniform segregated st ack column structure. DMTSA denotes 2,3-dimethyltetraselenoanthracene. The NO3 salt is semiconducting below room temperature, and the BF4 sa lt is metallic above 220 K and semiconducting at lower temperatures. W e found that their magnetic susceptibility is paramagnetic and indepen dent of temperature from 300 K down to 10 K in common. The obtained ma gnetic property can not be attributed to conduction electrons but disc ussed in terms of Mott insulating state. Furthermore, high pressure ex periment reveals that the NO3 salt is not semiconducting but rather se mi-metallic, and more that the BFq salt shows a small conductive anoma ly around 70 K and maintains metallic at low temperatures under the pr essure of 0:5 GPa.