NEW FEATURES OF THE ELECTRONIC PHASE-TRANSITION OBSERVED FOR GRAPHITE IN HIGH MAGNETIC-FIELDS

We have measured the magneto-resistance in single crystal graphite in pulsed high magnetic fields up to 52 T at low temperatures. When the magnetic field was applied parallel to the c-axis, many new features were found in the high field phase after the field-induced electronic phase transition. After a sharp rise at the phase transition, the resistance shows a dramatic decrease with increasing field, indicating the re-entrant character of the phase boundary. Fine structures consisting of local maxima were observed in the high field phase. Also observed was a prominent frequency dependence of the real and imaginary parts of the AC magneto-resistance, suggesting the validity of the pinned CDW model.