  Nonreciprocal resistance, depending on both directions of current ($j$) and
magnetic-field ($H$) or magnetization ($M$), is generally expected to emerge in
a chiral conductor, and be maximized for $j$ $\parallel$ $H$($M$). This
phenomenon, electrical magnetochiral effect (eMChE), is empirically known to
increase with $H$ in a paramagnetic or fully ferromagnetic state on chiral
lattice or to depend on fluctuation properties of a helimagnetic state. We
report here the eMChE over a wide temperature range in the chiral-lattice
magnet MnGe in which the spin hedgehog lattice (HL) forms with the triple
spin-helix modulation vectors. The magnitude of nonreciprocal resistivity is
sharply enhanced in the course of the field-induced structural transition of HL
from cubic to rhombohedral form. This is attributed to the enhanced asymmetric
electron scatterings by vector spin chirality in association with the large
thermal fluctuations of spin hedgehogs.
