The astrophysical S-factor for 4He-3He radiative capture is calculated at very low-energies. We construct conserved two- and three-body electromagnetic currents, using minimal substitution in the explicit momentum dependence of the two- and three-cluster interactions. The realistic Argonne v 18two-nucleon and Urbana IX or Tucson-Melbourne three-cluster interactions are considered for calculation. The zero energy S-factor is found to be S(0)=0.563 (0.581) keV b, with (without) three-body interactions, in satisfactory agreement with other theoretical results and experiment data.
