N=4 central charge superspace at work for supergravity coupled to an   arbitrary number of abelian vector multiplets
  We present the description in central charge superspace of N=4 supergravity with antisymmetric tensor coupled to an arbitrary number of abelian vector multiplets. All the gauge vectors of the coupled system are treated on the same footing as gauge fields corresponding to translations along additional bosonic coordinates. It is the geometry of the antisymmetric tensor which singles out which combinations of these vectors belong to the supergravity multiplet and which are the additional coupled ones. Moreover, basic properties of Chapline-Manton coupling mechanism, as well as the SO(6,n)/SO(6)*SO(n) sigma model of the Yang-Mills scalars are found as arising from superspace geometry. 
Sebastien Gurrieri and Annamaria Kiss