We show that the isotropic conductivity in the normal state of rare-earth tritelluride $R{\mathrm{Te}}_3$ compounds is broken by the occurrence of the unidirectional charge density wave (CDW) in the ($a$, $c$) plane below the Peierls transition temperature. In contrast with quasi-one-dimensional systems, the resistivity anomaly associated with the CDW transition is strong in the direction perpendicular to the CDW wave vector $\mathbf{Q}$ ($a$ axis) and very weak in the CDW wave vector $\mathbf{Q}$ direction ($c$ axis). We qualitatively explain this result by calculating the electrical conductivity for the electron dispersion with momentum-dependent CDW gap as determined by angle-resolved photoemission spectroscopy. Similar measurements of in-plane conductivity may uncover the gap anisotropy in other compounds for which angle-resolved photoemission spectroscopy is not available.

• Received 19 June 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.036601