  The X-ray spectra of serendipitously observed AGN in the XMM-Newton fields of
Mrk 205 and QSO 0130-403 are analysed. The sample consists of 23 objects, none
of which is detected at radio frequencies, with a median X-ray luminosity of ~
4 x 10^44 erg s^-1 and redshifts ranging from ~0.1 to just over 3. The mean
photon index was found to be 1.89 +/- 0.04. In contrast to past ASCA and ROSAT
observations of high-redshift radio-loud quasars, we find little evidence for
excess intrinsic absorption in these radio-quiet objects, with only three
sources requiring a column density in excess of the Galactic value. Comparing
the measured spectral indices over the redshift range, we also find there is no
X-ray spectral evolution of QSOs with time, up to redshift 3. Within the sample
there is no evidence for evolution of the optical to X-ray spectral index,
alpha-ox, with redshift, the mean value being -1.66 +/- 0.04. However, upon
comparing the values from the Bright Quasar Survey at low redshift (z < 0.5)
and high redshift QSOs detected by Chandra (z > 4), a slight steepening of
alpha-ox is noted for the more distant objects. In most of the sources there is
no significant requirement for a soft excess, although a weak thermal component
(< 10% of Lx) cannot be excluded. There is an indication of spectral flattening
(by delta gamma=0.2) at higher energies (> 3 keV, QSO rest frame) for the
sample as a whole. This is consistent with the presence of a Compton reflection
component in these radio-quiet AGN, with the scattering medium (such as an
accretion disc or molecular torus) occupying a solid angle of 2 pi steradians
to the X-ray source.
