  The equation of the spin-$\frac{1}{2}$ particles in the
Friedmann-Lema\^itre-Robertson-Walker spacetime is investigated. The retarded
and advanced fundamental solutions to the Dirac operator and generalized Dirac
operator as well as the fundamental solutions to the Cauchy problem are written
in explicit form via the fundamental solution of the wave equation in the
Minkowski spacetime.
