  The relativistic theory of above-threshold ionization (ATI) of hydrogen-like
atoms in ultrastrong radiation fields, taking into account the photoelectron
induced rescattering in the continuum spectrum is developed. It is shown that
the contribution of the latter in the multiphoton ionization probability even
in the Born approximation by Coulomb field is of the order of ATI probability
in the scope of Keldysh-Faisal-Reiss ansatz.
