  We present a detailed analysis of the overdensity of X-ray sources colse to
the 3C 295 galaxy cluster (z=0.46) to assess whether it is associated with a
filament of the large-scale structure of the Universe. We obtained optical
spectra of the optical counterparts of eleven sources associated with the
filament, finding that one is at z=0.474. This is a type 1 AGN at 1.5 arcmin
from the cluster center. We found three more sources with a redshift in the
range 0.37 - 0.53. We extracted the stacked X-ray spectrum of 47 X-ray sources
belonging to the putative filament. We found a significant narrow (at the
resolution of the Chandra ACIS-I) line at E ~ 4.4 keV, the energy of the iron
Kalpha line at the redshift of the cluster. The detection of this line is
confirmed at a confidence level of better than 3sigma and its energy is
constrained to be in the range 6.2--6.47 (at a 90% confidence level), excluding
an identification with the 6.7 helium-like iron line from the hot cluster ICM
at better than 4 sigma. We conclude that the detection of the redshifted line
is a strong indication that at least several of the excess sources lie at z ~
0.46 and that AGNs are efficient tracers of the ``filament'' connected with the
central cluster of galaxies.
