A striking nonlinear transport behavior has been observed in the recently discovered high-magnetic-field phase of graphite. The phenomenon is reminiscent of the collective charge-density-wave transport observed in some classes of linear-chain compounds such as NbSe3. This supports our identification of the new phase with a charge-density-wave state. The principal direction of the charged-density wave vector is perpendicular to the magnetic field in contrast to the prediction of the Yoshioka-Fukuyama theory. © 1985 The American Physical Society.