Low-Temperature Metallic Behavior and Resistance Minimum in a New Quasi One-Dimensional Organic Conductor

The dc and microwave conductivities of the new organic charge-transfer salt hexamethylene-tetraselenafulvalinium tetracyanoquinodimethanide (HMTSF-TCNQ) remain metallic in magnitude to temperatures at least as low as 1.1 K. At low $T$ we observe a resistance minimum and thermoelectric anomaly consistent with the theoretical result that density fluctuations can enhance the resistivity of a one-dimensional metal as $T\to 0$. Implications for ${\left(\mathrm{SN}\right)}_x$ and tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) are discussed.