  We report the discovery of a new AM Herculis system as the counterpart of the
bright and very soft X-ray source RX J0803.4-4748 found serendipitously in a
ROSAT PSPC pointing. Optical photometry showed deep (2 mag) variations with a
period of ~137 min placing RX J0803.4-4748 right into the period gap. The
modulation can be interpreted in terms of cyclotron beaming and is very similar
to that of other non-selfeclipsing polars like e.g. V843 Cen. Such a geometry
is also supported by the X-ray light curve of a later HRI pointing which was
lacking any pronounced faint-phase. Phase-resolved optical spectra are
charaterized by strong Balmer and HeII 4686 Angstroem line emission
superimposed onto a blue continiuum, and reveal disinct cyclotron humps at
certain phases. The field strength of 39 MG as derived from the separation of
the harmonics is in agreement with that of other soft X-ray polars.
