  The local spectroscopic signatures of metamagnetic criticality in Sr3Ru2O7
were explored using scanning tunneling microscopy (STM). Singular features in
the tunneling spectrum were found close to the Fermi level, as would be
expected in a Stoner picture of itinerant electron metamagnetism. These
features showed a pronounced magnetic field dependence across the metamagnetic
critical point, which cannot be understood in terms of a naive Stoner theory.
In addition, a pseudo-gap structure was observed over several tens of meV,
accompanied by a c(2x2) superstructure in STM images. This result represents a
new electronic ordering at the surface in the absence of any measurable surface
reconstruction.
