Anomalous transport properties of a linear-chain metal: Nb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Se</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

The transport properties of the linear-chain metal Nb${\mathrm{Se}}_{3}$ are anomalous. Giant increases in the dc resistivity appear at 145 and 59 K, suggestive of charge-density-wave (CDW) formation. These anomalies show breakdown effects with applied electric fields as low as 0.1 V ${\mathrm{cm}}^{\ensuremath{-}1}$. The temperature dependence of the resistivity also shows strong variation at microwave frequencies. We report measurements on the temperature dependence of the non-Ohmic effect together with microwave results and review the evidence for CDW formation. On the basis of the CDW model we have extracted a parameter $\ensuremath{\alpha}$ from the data which gives the fraction of the Fermi surface destroyed by the CDW gap. Other models are discussed and compared with the CDW model. We consider the possibility that the anomalous conductivity may arise from nonlinear excitations of a pinned CDW.

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