  We show an improved global well-posedness result for the Zakharov system in
two space dimensions with minimal regularity assumptions for the data.
Especially we are able to allow Schroedinger and wave data, which do not belong
to H^1 and L^2, respectively, thus with infinite energy. The proof uses a
refined I-method originally initiated by Colliander, Keel, Staffilani, Takaoka
and Tao and bilinear estimates by Bejenaru, Herr, Holmer and Tataru. A
polynomial growth bound for the solution is also given.
