  The effect of electron-electron interaction on the low-temperature
conductivity of graphene is investigated experimentally. Unlike in other
two-dimensional systems, the electron-electron interaction correction in
graphene is sensitive to the details of disorder. A new temperature regime of
the interaction correction is observed where quantum interference is suppressed
by intra-valley scattering. We determine the value of the interaction
parameter, F_0 ~ -0.1, and show that its small value is due to the chiral
nature of interacting electrons.
