  We report on the XMM-Newton (XMM) observation of RXJ1053.7+5735, one of the
most distant X-ray selected clusters of galaxies, which also shows an unusual
double-lobed X-ray morphology, indicative of a possible equal-mass cluster
merger. The cluster was discovered during the ROSAT deep pointings in the
direction of the Lockman Hole. All XMM Lockman Hole observations (PV, AO-1 &
AO-2 phases) with the European Photon Imaging Camera (EPIC) were combined for
the analysis, totaling exposure times ~ 648 ks, 738 ks, and 758 ks for pn,
MOS1, and MOS2, respectively. With this 'deep' dataset, we could detect the Fe
K line and obtain a strong constraint on cluster metallicity, which is
difficult to achieve for clusters at z > 1. The best-fit abundance is 0.46
+0.11/-0.07 times the solar value. The Fe line emission also allows us to
directly estimate the redshift of diffuse gas, with a value z = 1.14
+0.01/-0.01. This is one of the first clusters whose X-ray redshift is directly
measured prior to the secure knowledge of cluster redshift by optical/NIR
spectroscopy. We could also estimate the X-ray redshift separately for each of
the two lobes in the double-lobed structure, and the result is consistent with
the two lobes being part of one cluster system at the same redshift. Comparison
with other metallicity measurements of nearby and distant clusters shows that
there is little evolution in the ICM metallicity from z ~ 1 to the present.
