Gate-Tunable Unconventional Unidirectional Magnetoresistance in Chiral Tellurium Nanosheets.

Chiral materials, which lack inversion and mirror symmetries, host spin textures in momentum space that give rise to current-induced spin polarization. In bulk Te, symmetry restricts the induced spin polarization to the chiral axis, allowing unidirectional magnetoresistance (UMR) only when the magnetic field is aligned with this direction. Here, we demonstrate an unconventional UMR in chiral Te nanosheets that emerges under a magnetic field transverse to the chiral axis. The unconventional UMR exhibits nearly linear magnetic-field and current dependences and reverses sign with opposite crystal handedness, confirming its intrinsic chiral origin. First-principles calculations explain the unconventional UMR by out-of-plane spin polarization induced by symmetry reduction in Te nanosheets. Furthermore, electrostatic gating experiments demonstrate that the unconventional UMR is governed by the electronic structure near the Fermi level. These results establish symmetry reduction and Fermi-level control as effective routes to generating multiaxis spin polarization in chiral materials.