A model of the nominal term structure of interest rates is developed that
has a conditional variance whose process follows a nonlinear GARCH process. As a
quadratic 2-factor model, this model delivers analytical approximation formula for
the prices and yields-to-maturity of default-free bonds. Furthermore, the
comparison of the yield volatility of On-the-Run Treasuries with the volatility
curve of our model implies that it is of importance to take into account moments
for volatility curves as well as yield curves.

