  In single crystals of SrTiO_3, a paramagnetic center, characterized by S =
3/2 and hyperfine interaction with an I = 5/2 nuclear spin has been observed in
the temperature range 4.2K-77K by means of EPR. The impurity center is
attributed to Mo3+. No additional line splitting in the EPR spectrum due to the
105K phase transition has been observed. At 4.2K the following spin Hamiltonian
parameters for this impurity ion were obtained: g = 1.9546\pm0.0010 and A =
(32.0\pm0.05)\times10^-4 cm^-1.
