  A new approach to the two-body problem based on the extension of the
$SL(2,C)$ group to the $Sp(4,C)$ one is developed. The wave equation with
various forms of including the interaction for the system of the spin-1/2 and
spin-0 particles is constructed. For this system, it was found that the wave
equation with a linear confinement potential involved in the non-minimal manner
has an oscillator-like form and possesses the exact solution.
