13-04U

Interaction of scalar particles via tachyon field is considered within the partially reduced field theory. The differential and integral cross-sections of elastic scattering of two different particles interact\-ing via mediating field of imaginary mass are calculated. A Salpeter-type equation for bound states and then the non-relativistic potential of tachyon interaction has been derived. The Schr\"odinger equation with this potential is studied by means of various approximations. The condition for existence of bound states is analyzed.