  The Vela supernova remnant displays several ejecta, which are fragment-like
features protruding beyond the front of its primary blast shock wave. They
appear to be "shrapnel", bowshock-shaped relics of the supernova explosion. One
of these pieces of shrapnel (A), located in the northeastern edge of the
remnant, is peculiar because its X-ray spectrum exhibits a high Si abundance,
in contrast to the other observed ejecta fragments, which show enhanced O, Ne,
and Mg abundances. We present the analysis of another fragment located opposite
to shrapnel A with respect to the center of the shell, in the southwestern
boundary of the remnant, named shrapnel G. We thoroughly analyzed a dedicated
XMM-Newton observation of shrapnel G by producing background-subtracted and
exposure-corrected maps in different energy ranges, which we complemented with
a spatially resolved spectral analysis of the X-ray emission. The fragment
presents a bowshock-like shape with its anti-apex pointing to the center of the
remnant. Its X-ray spectrum is best fit by a thermal plasma out of equilibrium
of ionization with low O and Fe, roughly solar Ne and Mg, and a significantly
high Si abundance, which is required to fit a very clear Si line at ~1.85 keV.
Its chemical composition and spectral properties are compatible with those of
shrapnel A, which is located on the opposite side of the remnant. As a
consequence of the nucleosynthesis, pieces of Si-rich shrapnel are expected to
originate in deeper layers of the progenitor star compared to ejecta with
lower-Z elements. A high velocity and density contrast with respect to the
surrounding ejecta are necessary to make shrapnel A and G overtake the forward
shock. The line connecting shrapnel A and G crosses almost exactly the
expansion center of the remnant, strongly suggesting a Si-rich jet-counterjet
structure, reminiscent of that observed in the young remnant Cas A.
