  The phase structure of four-dimensional simplicial quantum gravity coupled to
U(1) gauge fields has been studied using Monte-Carlo simulations. The smooth
phase is found in the intermediate region between the crumpled phase and the
branched polymer phase. This new phase has a negative string susceptibility
exponent, even if the number of vector fields (Nv) is 1. The phase transition
between the crumpled phase and the smooth phase has been studied by a finite
size scaling method. From the numerical results, we expect that this model
(coupled to one gauge field) has a higher order phase transition than first
order, which means the possibility to take the continuum limit at the critical
point. Furthermore, we consider a modification of the balls-in-boxes model for
a clear understanding of the relation between the numerical results and the
analytical one.
