Weak Localization in Graphite

Conductivity and magnetoconductivity have been measured for various kinds of graphite crystals at low temperatures down to 0.03 K. Anomalous behaviours have been found in polycrystalline (but well oriented) specimens of graphite. At low temperatures below 0.1 K, the conductivity shows T 1/2 dependence in and without magnetic field, Anisotropic magnetoconductivity is observed. It varies as H 1/2 , with the sign which changes from negative to positive with increasing magnetic field strength. These behaviors are fairly well explained in terms of localization and electron-electron interaction in the three-dimensional weakly localized regime. The inelastic scattering time τ ε shows a little weaker temperature dependence than T -1 .