  The properties of the equation of Dirac type in three-dimensional and
five-dimensional Minkowski space-time with respect to time reflection (in sense
of Pauli and Wigner) as well as to the operation of charge conjugation are
investigated. P-, T-, C-invariance of Dirac equation for the cases of four
components (in three-dimentional space) and eight components (in
five-dimensional space) is established. Within the framework of the Poincare
group a relativistic equation is suggested wich describes the movement of a
particle with non-fixed (indefinite) mass in external electromagnetic field.
