Origin of the Anomalous Electrical Transports in Quasi-One-Dimensional Ta 2 NiSe 7 .

Exploration of exotic transport behavior is of great interest and importance for revealing the properties of the CDW phase of quasi-one-dimensional Ta 2 NiSe 7 . We report the anisotropic electrical transport properties of Ta 2 NiSe 7 single crystals in the CDW phase. The anisotropic constant (γ = ρ b /ρ c ) increased rapidly at T CDW = 60 K upon cooling. The results of the Hall resistivity show that both the concentrations and mobilities of carriers change abruptly at T CDW . The out-of-plane AMR exhibits C 2 and C 4 symmetry components while the in-plane AMR exhibits C 2 , C 4 , and C 6 at the CDW state. The planar Hall effect is observed in Ta 2 NiSe 7 at low temperature, which is suggested to originate from the anisotropic orbital magnetoresistance. The calculated results show that the Fermi surface of Ta 2 NiSe 7 was slightly reconstructed due to the CDW transition. This work highlights the enhancement of Fermi surface anisotropy during CDW formation and provides a novel approach to study the CDW materials.