  The low-energy electronic structure of the itinerant metamagnet Sr3Ru2O7 is
investigated by angle resolved photoemission and density functional
calculations. We find well-defined quasiparticle bands with resolution limited
line widths and Fermi velocities up to an order of magnitude lower than in
single layer Sr2RuO4. The complete topography, the cyclotron masses and the
orbital character of the Fermi surface are determined, in agreement with bulk
sensitive de Haas - van Alphen measurements. An analysis of the dxy band
dispersion reveals a complex density of states including van Hove singularities
(vHs) near the Fermi level; a situation which is favorable for magnetic
instabilities.
