The stability of large bipolarons in the presence of a static magnetic
field is investigated on the basis of Feynman's path-integral approac
h (although the region of validity of the Jensen-Feynman inequality re
mains to be investigated for bipolarons). We find that the magnetic fi
eld (characterized by the cyclotron frequency omega(c)) favors bipolar
on formation: (i) the critical electron-phonon coupling parameter alph
a(c) (above which the bipolaron is stable) decreases with increasing o
mega(c) and (ii) the critical Coulomb repulsion strenght U-c (below wh
ich the bipolaron is stable) increases with increasing omega(c). The b
inding energy and the corresponding variational parameters are calcula
ted as a function of alpha, U and omega(c).