  Resistive transitions have been measured on a perforated Nb thin film with a
lattice of holes with the period of the order of ten nanometers. Bumps in the
dR/dH versus H curves have been observed at the first matching field and its
fractional values, 1/4, 1/9 and 1/16. This effect has been related to different
vortex lattice configurations made available by the underlying lattice of
holes.
