Ultrahigh thermoelectric power factors and anisotropy in the quasi-1D metals Nb₃X₄ (X = S, Se)

We report measurements of electrical resistivity (ρ) and Seebeck coefficient (S) in the quasi-one-dimensional metals^a,b,c Nb₃X₄, X = S (Se), revealing ultrahigh power factors along their conducting chains, PF=S²/ρ=130 (340) μW/cm K² in the range 30 K ≤ T ≤ 75 K, among the largest reported for any material. Measurements perpendicular to the chains in Nb₃S₄ yield an even larger PF and demonstrate this compound to have p × n character, i.e. with S having opposite sign in mutually perpendicular directions.

^a E. Amberger {\it et al.} Sol. St. Commun. 26, 943 (1978).

^b Y. Ishihara and I. Nakada, Sol. St. Commun. 42, 579 (1982); ibid. 44, 1439 (1982).

^c Y. Ishihara {\it et al.} Sol. St. Commun. 50, 657 (1984).