Polytypism, Anisotropic Transport, and Weyl Nodes in the van der Waals Metal TaFeTe 4

Layered van der Waals (vdW) materials belonging to the 'Te structure class have recently received intense attention due to their ability to host exotic electronic transport phenomena, such as in-plane transport anisotropy, Weyl nodes, and superconductivity. Here we report two new vdW materials with strongly anisotropic in-plane structures featuring stripes of metallic TaTe and semiconducting FeTe , α-TaFeTe and β-TaFeTe . We find that the structure of α-TaFeTe produces strongly anisotropic in-plane electronic transport (anisotropy ratio of up to 250%), outcompeting all other vdW metals, and demonstrate that it can be mechanically exfoliated to the two-dimensional (2D) limit. We also explore the possibility that broken inversion symmetry in β-TaFeTe produces Weyl points in the electronic band structure. Eight Weyl nodes slightly below the Fermi energy are computationally identified for β-TaFeTe , indicating they may contribute to the transport behavior of this polytype. These findings identify the TaFeTe polytypes as an ideal platform for investigation of 2D transport anisotropy and chiral charge transport as a result of broken symmetry.