Using low-temperature scanning tunnelling spectroscopy we investigate elect
ron scattering from isolated Ce adatoms on Ag(111). dI/dV tunnelling spectr
a reveal a characteristic antiresonance around the Fermi energy which is no
t observed for nonmagnetic Ag adatoms. We interpret this spectrum as a Fano
interference between delocalised sp-derived Ag states and the localised f-
derived Kondo resonance.