N=2 Nonlinear Sigma Models in N=1 Superspace: Four and Five Dimensions
  We formulate four-dimensional N=2 supersymmetric nonlinear sigma models in N=1 superspace. We show how to add superpotentials consistent with N=2 supersymmetry. We lift our construction to higher-dimensional spacetime and write five-dimensional nonlinear sigma models in N=1 superspace. 
Jonathan Bagger and Chi Xiong