  Conventional phonon-electron interaction induces either triplet or one of two
(degenerate) singlet pairing states in time reversal and inversion invariant 3D
Dirac semi - metal. Investigation of the order parameters and energies of these
states at zero temperature in wide range of values of chemical potential $\mu
$, the effective electron-electron coupling constant $\lambda $ and Debye
energy $T_{D}$ demonstrates that when the exchange interaction is neglected the
singlet always prevails, however in significant portions of the $\left( \mu
,\lambda ,T_{D}\right) $ parameter space the energy difference is very small.
This means that interactions that are small but discriminate between the spin
singlet and the spin triplet are important in order to determine the nature of
the superconducting order there. The best candidate for such an interaction in
materials under consideration is the exchange (the Stoner term) characterized
by constant $\lambda _{ex}$. We show that at values of $\lambda _{ex}$ much
smaller then ones creating Stoner instability to ferromagnetism $\lambda
_{ex}\sim 1$ the triplet pairing becomes energetically favored over the singlet
ones for $\mu <T_{D}$% . The 3D quantum critical point at $\mu =0$ is
considered in detail.
