  We present systematic construction of probability and probability current
densities operators for one-band single particle Pauli equations starting from
the operators in Dirac electron model within Second Quantized Approach. These
operators are of importance as in probability interpretation of experimental
data, so in establishing of boundary conditions. It is shown that derived
operators differ significally from their convential Schrodinger-type
counterparts. The generalization of continuity equation for probability density
under external perturbations and physical meaning of additional source terms is
discussed. The presented approach can be useful in analysis of carriers
dynamics described within generic multicomponent $\vec{k} \cdot \vec{p}$
Hamiltonians in Envelope Function Approximation (EFA).
