  We construct a degeneration of the moduli space of Hitchin pairs on smooth
projective curves when the curve degenerates to an irreducible curve with a
single node. The degeneration constructed here is analogous to the models
constructed by Gieseker and Nagaraj-Seshadri for the case of the usual moduli
spaces (i.e when the Higgs structure is trivial). There is an canonical
relative Hitchin map which is shown to be proper and the general fibre of the
relative Hitchin map provides a new compactification of the Picard variety of
smooth curves with normal crossing singularities.
