  We show that the isotropic conductivity in the normal state of rare-earth
tritelluride RTe_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 Q (a-axis) and very weak in the CDW wave
vector 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 (ARPES).
