  Planar Topological Hall effect (PTHE) is known to arise from in-plane
skyrmion tubes with an external magnetic field applied in the plane of the
charge current. Here, we propose that the PTHE can robustly appear also from an
unexpected source, the conical spin spiral, realizable in a variety of
materials. We show that for both in-plane skyrmion tubes and conical spin
spirals, the PTHE is two-fold symmetric with respect to the magnetic-field
angle, while it is four-fold symmetric for 90$^{\circ}$-rotated domains of
conical spin spirals. We predict that the symmetry and magnetic-field response
of the PTHE can distinguish between the two scenarios, unambiguously probing
the nature of the antisymmetric spin-exchange interaction and the resulting
magnetic texture.
