  The extragalactic microquasar S26 has the most powerful jets observed in
accreting binaries, with a kinetic luminosity of $L_{\rm jet}\sim10^{40}\,{\rm
erg\,s^{-1}}$. According to the jet-disk symbiosis model, this implies that the
accretion power to the stellar black hole at the core of the system should be
very super-Eddington, on the order of $L_{\rm acc}\sim L_{\rm jet}$. However,
the observed X-ray flux of this system, measured by the \textit{Chandra} and
\textit{XMM-Newton} telescopes, indicates an apparent very sub-Eddington
accretion luminosity of $L_{\rm X}\approx 10^{37}\,{\rm erg\,s^{-1}}$, orders
of magnitude smaller than the jet power. We present here a preliminary
investigation of the relationship between jet and disk power, analyze an X-ray
observation of S26 obtained with \textit{XMM-Newton}, and propose an
explanation for the emission. We also examine the acceleration and distribution
of the particles to discuss the feasibility of microquasars as potential
PeVatron sources, exploring their ability to produce cosmic rays with energies
of about 1 PeV or higher.
