  The radio supernova remnant W50 hosts at its center the peculiar galactic
X-ray binary SS 433. It shows a central spherical structure with two `ears'
which are supposed to be formed by the interaction of the precessing jets of SS
433 with the supernova shell. In two pointings in September/October 2004 for 30
ks each the eastern jet of SS 433 was observed with XMM-Newton to study the
outermost parts of the `ear' and the X-ray bright emission region about 35
arcmin from SS 433. The spectra consist of two components: a non-thermal power
law with photon index \Gamma ~ 2.17+/-0.02 and a thermal component at a typical
temperature of kT ~ 0.3 keV. The X-ray emission seems to fill the whole
interior region of the radio remnant W50. The jet terminates in the eastern
`ear' in a ring-like terminal shock which indicates a flow with a kind of
hollow-cone morphology. The spatial coincidence of X-ray and radio emission
suggests physical conditions similar to those found at the outer shocks of
ordinary supernova remnants. The bright emission region closer to SS 433
radiates non-thermally in a spatially well confined geometry at higher X-ray
energies. At soft X-rays the shape of the region gets blurred, centered on the
hard lenticular emission. The shape of this region and the bend in the jet
propagation direction might be caused by the interaction of a re-collimated jet
with the outer, non homogeneous interstellar matter distribution. The physical
conditions leading to the re-collimation of the jet and the peculiar emission
morphology are far from being understood and require deeper observations as
well as a detailed modeling of the interaction of a jet with its surroundings.
