  When nanometric, noncoplanar spin textures with scalar spin chirality (SSC)
are coupled to itinerant electrons, they endow the quasiparticle wavefunctions
with a gauge field, termed Berry curvature, in a way that bears analogy to
relativistic spin-orbit coupling (SOC). The resulting deflection of moving
charge carriers is termed geometrical (or topological) Hall effect. Previous
experimental studies modeled this signal as a real-space motion of wavepackets
under the influence of a quantum-mechanical phase. In contrast, we here compare
the modification of Bloch waves themselves, and of their energy dispersion, due
to SOC and SSC. Using the canted pyrochlore ferromagnet Nd$_2$Mo$_2$O$_7$ as a
model compound, our transport experiments and first-principle calculations show
that SOC impartially mixes electronic bands with equal or opposite spin, while
SSC is much more effective for opposite spin band pairs.
