  Microquasars are Black Hole X-ray binaries (BHXB) which can eject material in
the form of a bipolar jet, similarly to quasars, but at much smaller scales.
Their high-energy emission comes from an accretion disk (~ 1 keV) and from a
hot "corona" near the black hole that up-scatters photons from the disk in the
hard X-ray domain (1--100 keV). A high-energy component above 150 keV has been
detected in bright sources and its precise origin is still unknown: it could
come either from Compton scattering of disk photons on coronal relativistic
non-thermal electrons (a.k.a hybrid Comptonization), or from the synchrotron
emission from the very base of the compact jet. The measurement of polarization
above 150 keV can provide valuable insights into the processes at play as we
expect higher polarization fraction due to synchrotron emission from the jets
(up to 70 % with a very ordered magnetic field). We use the INTEGRAL/IBIS
telescope to measure the soft gamma-ray polarization of the Crab Nebula and the
BHXB Swift J1727.8-1613.
