  We separate localization and interaction effects in epitaxial graphene
devices grown on the C-face of a 4H-SiC substrate by analyzing the low
temperature conductivities. Weak localization and antilocalization are
extracted at low magnetic fields, after elimination of a geometric
magnetoresistance and subtraction of the magnetic field dependent Drude
conductivity. The electron electron interaction correction is extracted at
higher magnetic fields, where localization effects disappear. Both phenomena
are weak but sizable and of the same order of magnitude. If compared to
graphene on silicon dioxide, electron electron interaction on epitaxial
graphene are not significantly reduced by the larger dielectric constant of the
SiC substrate.
