  The existence of helical surface states in a bulk insulator, with anomalous
magneto-electric properties, is a remarkable new development in solid state
physics. The linear dispersion of the the fermions leads to a form of Lorentz
invariance, with the Fermi velocity playing the role of the velocity of light
($c$). In a crossed electric and magnetic field the single particle states form
Landau levels whose energies can be changed by varying the applied
\emph{in-plane electric} field. The degeneracy remains constant and is
determined by the magnetic field. In the letter we study the nature of the
mangeto-oscillation in conductivity and thermopower as a function of the
\emph{in-plane electric} field.
