Evidence for weak antilocalization in epitaxial graphene*

Transport in ultrathin graphite on silicon carbide is graphene-like and appears to be dominated by the electron-doped epitaxial graphene layer at the interface. Weak antilocalization in 2D samples manifests itself as a broad cusp-like depression in the longitudinal resistance for magnetic fields 10 mT $<$ B $<$ 5 T. An extremely sharp weak-localization resistance peak at B = 0 is also observed. These features quantitatively agree with recent graphene weak-localization theory. Scattering contributions from charges in the substrate and from trigonal warping due to the graphite layer are tentatively identified. The Shubnikov-de Haas oscillations show an anomalous Berry's phase. Their small amplitudes may be related to graphene scattering processes.