  Ionization of hydrogen-like ions by intense, circularly polarized laser
pulses is analyzed under the scope of the relativistic strong-field
approximation. We show that, for specific parameters of the laser field, the
energy spectra of photoelectrons present a broad region without interference
(supercontinuum) which can be controlled by modifying the laser field
intensity. The physical interpretation of the process is developed according to
the Keldysh theory, emphasizing the importance of the complex-time saddle point
contributions to the total probability of photoionization. The corresponding
polar-angle distributions present an asymmetry attributed to radiation pressure
effects.
