  XMM-Newton observed SAX J2103.5+4545 on January 6, 2003, while RXTE was
monitoring the source. Using RXTE-PCA dataset between December 3, 2002 and
January 29, 2003, the spin period and average spin-up rate during the
XMM-Newton observations were found to be $354.7940\pm0.0008$ s and
$(7.4\pm0.9)\times10^{-13}$Hz s$^{-1}$ respectively. In the power spectrum of
the 0.9-11 keV EPIC-PN lightcurve, we found quasi periodic oscillations around
0.044 Hz (22.7 s) with an rms fractional amplitude $\sim $6.6 %. We interpreted
this QPO feature as the Keplerian motion of inhomogenuities through the inner
disk. In the X-ray spectrum, in addition to the power law component with high
energy cutoff and $\sim6.4$ keV fluorescent iron emission line (Baykal et al.,
2002), we discovered a soft component consistent with a blackbody emission with
${\rm{kT}}\sim1.9$keV. The pulse phase spectroscopy of the source revealed that
the blackbody flux peaked at the peak of the pulse with an emission radius
$\sim 0.3$ km, suggesting the polar cap on the neutron star surface as the
source of blackbody emission. The flux of the iron emission line at $\sim 6.42$
keV was shown to peak at the off-pulse phase, supporting the idea that this
feature arises from fluorescent emission of the circumstellar material around
the neutron star rather than the hot region in the vicinity of the neutron star
polar cap.
