  Magnetic skyrmions were thought to be stabilised only in inversion-symmetry
breaking structures, but skyrmion lattices were recently discovered in
inversion symmetric Gd-based compounds, spurring questions of the
stabilisationmechanism. A natural consequence of a recent theoretical proposal,
a coupling between itinerant electrons and localised magnetic moments, is that
the skyrmions are amenable to detection using even non-magnetic probes such as
spectroscopic-imaging scanning tunnellingmicroscopy (SI-STM). Here SI-STM
observations of GdRu$_2$Si$_2$ reveal patterns in the local density of states
that indeed vary with the underlying magnetic structures. These patterns are
qualitatively reproduced by model calculations which assume exchange coupling
between itinerant electrons and localised moments. These findings provide a
clue to understand the skyrmion formation mechanism in GdRu$_2$Si$_2$.
