Electrical resistivity of single-crystal graphite under pressure: An anisotropic three-dimensional semimetal

Abstract

The in-plane $\left({\rho }_a\right)$ and $c$-axis $\left({\rho }_c\right)$ resistivities of natural single-crystal graphite have been measured from 4 to 450 K at zero pressure and from 77 to 450 K under pressures up to 500 MPa. Data for ${\rho }_c$ differ strongly from earlier results obtained on synthetic graphite in showing a strong $T$ dependence of the pressure coefficient, while data for ${\rho }_a$ agree well with those from previous studies. Our results can be analyzed quantitatively in a simple free-electron model, and we conclude that in contrast to quasi-two-dimensional synthetic graphite, natural single-crystal graphite is an anisotropic three-dimensional semimetal.