  Magneto-transport properties have been investigated for epitaxial thin films
of B20-type MnSi grown on Si(111) substrates. Both Lorentz transmission
electron microscopy (TEM) images and topological Hall effect (THE) clearly
point to the robust formation of skyrmions over a wide temperature-magnetic
field region. New features distinct from those of bulk MnSi are observed for
epitaxial MnSi films: a shorter (nearly half) period of the spin helix and
skyrmions, and an opposite sign of THE. These observations suggest versatile
features of skyrmion-induced THE beyond the current understanding.
