Extended Data Fig. 1: Helicoid arc dispersion along closed contours in RhSi.

a, Surface-sensitive ARPES measured Fermi surface map of RhSi. Encircling the \(\bar{{{\Gamma }}}\)- and \(\bar{{{{\rm{M}}}}}\)-pockets are dashed-line loops of different radii. b, Energy-momentum cuts along the inner (left panel; orange dashed- line) and outer (right panel; black dashed-line) circular loops resolve a net number of two left-moving chiral modes, corresponding to a projected chiral charge C = − 2 at the \(\bar{{{{\rm{M}}}}}\)-pockets. The inner and outer loops have radius 0.18 Å⁻¹ and 0.23 Å⁻¹, respectively. c, d Energy-momentum cuts along the inner and outer (panel d) circular loops resolve a net number of two right-moving chiral modes, corresponding to a projected chiral charge C = + 2 at the \(\bar{{{\Gamma }}}\)-pocket. The inner and outer loops have radius 0.3 Å⁻¹ and 0.4 Å⁻¹, respectively. Guides for the eye (green dashed lines) track the chiral modes.