Thermopower and electrical resistivity measurements transverse to the conducting chains of the quasi-one-dimensional metal Li0.9Mo6O17 are reported in the temperature range 5≤T≤500  K. For T≥400  K the interchain transport is determined by thermal excitation of charge carriers from a valence band ∼0.14  eV below the Fermi level, giving rise to a large, p-type thermopower that coincides with a small, n-type thermopower along the chains. This dichotomy-semiconductorlike in one direction and metallic in a mutually perpendicular direction-gives rise to substantial transverse thermoelectric effects and a transverse thermoelectric figure of merit among the largest known for a single compound.

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Transport measurements (electrical resistivity, Seebeck coefficient, and thermal conductivity) in the temperature range 80-500 K are presented for single crystals of the quasi-one-dimensional (Q1D) semiconductor Li 0.33 MoO 3. Opposite signs are observed for the Seebeck coefficient along the trinclinic a and c axes, with S c À S a ' 250 lV/K near room temperature and '100 lV/K at 380 K. The thermal conductivity at room temperature in the a-c planes was $2 W/m K and $10 times smaller along b*. A weak structural anomaly at T s % 355 K, identified in the temperaturedependent lattice constants, coincides with anomalies in the electrical properties. Analysis of the electronic transport at T > T s favors an intrinsic semiconductor picture for transport along the most conducting Q1D axis and small-polaronic transport along the other directions, providing insight into the origin of the Seebeck anisotropy. V

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