Negative c-axis magnetoresistance in graphite

We have studied the c  -axis interlayer magnetoresistance (ILMR), Rc(B)Rc(B) in graphite. The measurements have been performed on strongly anisotropic highly oriented pyrolytic graphite (HOPG) and single crystalline Kish graphite samples in magnetic field up to B=9 TB=9 T, and the temperature interval 2 K⩽T⩽300 K2 K⩽T⩽300 K. We have observed negative magnetoresistance, dRc/dB<0dRc/dB<0, for B‖cB‖c-axis for both samples above a certain field Bm(T)>5.4 TBm(T)>5.4 T and 0.2 T for HOPG and Kish graphite, respectively. The results can be understood consistently by assuming that ILMR is related to a tunneling between zero-energy Landau levels of quasi-two-dimensional Dirac fermions, in a close analogy with the behavior reported for α-(BEDT-TTF)2I3 [N. Tajima, et al., Phys. Rev. Lett. 102 (2009) 176403], another multilayer Dirac electron system.