Spin-valve effect for spin-polarized surface states in topological semimetals

We experimentally investigate magnetoresistance of a single GeTe-Ni junction between the $\alpha$-GeTe topological semimetal and thick nickel film at room and liquid helium temperatures. For the magnetic field parallel to the junction plane, we demonstrate characteristic spin-valve hysteresis with mirrored differential resistance $dV\mathrm{/}dI$ peaks even at room temperature. In contrast, for normal magnetic fields spin-valve effect appears only at low temperatures. From the magnetic field anisotropy, observation of the similar effect for another topological semimetal Cd${}_3$As${}_2$, and strictly flat $dV\mathrm{/}dI(H)$ magnetoresistance curves for the reference GeTe-Au junction, we connect the observed spin-valve effect with the spin-dependent scattering between the spin textures in the topological surface states and the ferromagnetic nickel electrode. For the topological semimetal $\alpha$-GeTe, room-temperature spin-valve effect allows efficient spin-to-charge conversion even at ambient conditions.