Comment on "Nonexistence of "Spin Transverse Force" for a Relativistic Electron" by Wlodek Zawadzki (cond-mat/0701387)

This is a reply to W. Zawadzki's paper (arXiv: cond-mat/0701378) on non-exietence of spin transverse force for a relativistic electron. The force was first proposed by the present author that the spin current will experience a transverse force in an electric field as a relativistic quantum mechanical effect, and in semiconductor with Rahsba spin-orbit coupling. Zawadzki's approach is based on an incorrect relation between the velocity and canonical momentum, and his conclusion is not true.