  The Zeeman interaction results in spontaneous current through a Josephson
contact with a spin-orbit coupled normal metal, even in the absence of any
voltage, or phase bias. In the case of the Rashba spin orbit coupling of
electrons in a two-dimensional (2D) electron gas this effect takes place for
the Zeeman field which is parallel to the 2D system and to superconducting
contacts. At the same time, the spontaneous current is absent when this field
is perpendicular to the contacts. It is shown that in the latter case it may
manifest itself in oscillations of the critical Josephson current at the
varying Zeeman energy. These oscillations have a form of the Fraunhofer
diffraction pattern. The Josephson current under the phase bias was calculated
based on the semiclassical Green functions for a disordered 2D electron gas
with the strong spin orbit coupling, as well as for surface electrons of a
three dimensional topological insulator. In the latter case the diffraction
pattern was found to be most pronounced, while in the Rashba gas the
oscillations of the critical current are weaker.
