Negative c-axis Magnetoresistance in Graphite

Aiming to verify the possible behavior of graphite as a stack of graphene layers, we have studied in this work the c-axis (interlayer) magnetoresistance (ILMR), R$_{c}$(B). The measurements have been performed on strongly anisotropic highly oriented pyrolytic graphite samples in magnetic field of up to B = 9T applied both parallel and perpendicular to the sample c-axis, and temperatures 2 K $\le $ T $\le $ 300 K. We observed the negative magnetoresistance (MR), dR$_{c}$/dB $<$ 0, for B$\vert \vert $c above a certain field B$_{m}$(T) that reaches its minimum value B$_{m}$ = 5.4 T at T = 150 K. The results can be consistently understood 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 $\alpha $-(BEDT-TTF)$_{2}$I$_{3}$ [N. Tajima et al., Phys. Rev. Lett. 102, 176403 (2009)], another multilayer Dirac electron system.