  A concise geometrical formulation of N=4 supergravity containing an
antisymmetric tensor gauge field is given in central charge superspace:
graviphotons are identified in the super-vielbein on the same footing as the
vierbein and the Rarita-Schwinger fields. As a consequence of superspace
soldering, Chern-Simons terms in the fieldstrength of the antisymmetric tensor
arise as an intrinsic property of superspace with central charge coordinates.
