  We consider a system of interacting spinor and scalar fields in a
gravitational field given by a Bianchi type-I cosmological model filled with
perfect fluid. The interacting term in the Lagrangian is chosen in the form of
derivative coupling, i.e., ${\cal L}_{\rm int} = \frac{\lambda}{2}
\vf_{,\alpha}\vf^{,\alpha} F$, with $F$ being a function of the invariants $I$
an $J$ constructed from bilinear spinor forms $S$ and $P$. We consider the
cases when $F$ is the power or trigonometric functions of its arguments.
Self-consistent solutions to the spinor, scalar and BI gravitational field
equations are obtained. The problems of initial singularity and asymptotically
isotropization process of the initially anisotropic space-time are studied. It
is also shown that the introduction of the Cosmological constant
($\Lambda$-term) in the Lagrangian generates oscillations of the BI model,
which is not the case in absence of $\Lambda$ term. Unlike the case when spinor
field nonlinearity is induced by self-action, in the case in question, wehere
nonlinearity is induced by the scalar field, there exist regular solutions even
without broken dominant energy condition.
