Fig. 2. The second-harmonic Hall effect near the transition temperature.

(A) Magnetic field dependence of the real part of second-harmonic Hall resistivity (Re ${\mathrm{\rho }}_{\mathit{z}\mathit{x}}^{2\mathit{f}}$) measured with current densities j = 2.1 × 10⁸ A/m² (blue lines) and j = 8.3 × 10⁸ A/m² (red lines). The blue, orange, green, and white shadows represent helical, SkL, conical, and ferromagnetic phases, respectively. (B) Contour mapping of Re ${\mathrm{\rho }}_{\mathit{z}\mathit{x}}^{2\mathit{f}}$ in the temperature–magnetic field plane. The blue, green, and red circles denote helical-to-conical, conical-to-ferromagnetic, and SkL-to-conical phase transitions, respectively, determined from kinks in the magnetic field dependence of planar linear Hall resistivity. The green squares represent helical, conical, and SKL-to-paramagnetic phase transitions determined from inflection points of the temperature dependence of longitudinal resistivity (see also the Supplementary Materials).