Abstract
Unidirectional magnetoresistance, or electric magnetochiral anisotropy (eMChA), is a nonlinear magnetotransport phenomenon that arises in noncentrosymmetric conductors , where changes in resistance R(B) are: (i) chiral, Δ R(B)/R(0)=2χ I· B, or (ii) polar, Δ R(B)/R(0)=2γ I·( P× B), with eMChA coefficients χ and γ. In [Phys. Rev. Lett. 135, 106602 (2025)], we showed that the eMChA in the conduction band of tellurene is polar (χ=0, γ≠ 0) and emerges from the quantum metric dipole due to its Weyl node and from the lone pair polarization P. Here, we extend our work to the valence band of tellurene, where the eMChA is usually said to be chiral (χ ≠ 0, γ = 0). We show that also a polar coefficient γ ≠ 0 emerges naturally through a downfolding procedure, in which remote Weyl-node containing bands induce momentum-space gradients of the quantum metric in the low-energy levels, activating finite metric dipoles. Combining semiclassical Boltzmann transport with a k· p description of tellurene, our numerical calculations agree quantitatively with doping (μ) dependent second-harmonic measurements of the longitudinal voltage V^2ω_∥(μ) in perpendicular field. The combined chiral and polar characters (χ≠0, γ≠ 0) of the eMChA in tellurene also explains the shift in the angular (φ) dependence of V^2ω_∥(φ) for in plane fields. Our results demonstrate that the polar eMChA can arise in topologically trivial bands through multiband effects and establishes tellurene as a platform for quantum-geometric rectification in both electron and hole regimes.