  Multi-component dark matter scenarios constitute natural extensions of
standard single-component setups and offer attractive new dynamics that could
be adopted to solve various puzzles of dark matter. In this work we present and
illustrate properties of a minimal UV-complete vector-fermion dark matter model
where two or three dark sector particles are stable. The model we consider is
an extension of the Standard Model (SM) by spontaneously broken extra $U(1)_X$
gauge symmetry and a Dirac fermion. All terms in the Lagrangian which are
consistent with the assumed symmetry are present, so the model is
renormalizable and consistent. To generate mass for the dark-vector $X_\mu$ the
Higgs mechanism with a complex singlet $S$ is employed in the dark sector. Dark
matter candidates are the massive vector boson $X_\mu$ and two Majorana
fermions $\psi_\pm$. All the dark sector fields are singlets under the SM gauge
group. The set of three coupled Boltzmann equations has been solved numerically
and discussed. We have performed scans over the parameter space of the model
implementing the total relic abundance and direct detection constraints. The
dynamics of the vector-fermion dark matter model is very rich and various
interesting phenomena appear, in particular, when the standard annihilations of
a given dark matter are suppressed then the semi-annihilations, conversions and
decays within the dark sector are crucial for the evolution of relic abundance
and its present value. Possibility of enhanced self-interaction has been also
discussed.
