  We present a superconformal master action for a class of supergravity models
with one arbitrary function defining the Jordan frame. It leads to a
gauge-invariant action for a real vector multiplet, which upon gauge fixing
describes a massive vector multiplet, or to a dual formulation with a linear
multiplet and a massive tensor field. In both cases the models have one real
scalar, the inflaton, naturally suited for single-field inflation. Vectors and
tensors required by supersymmetry to complement a single real scalar do not
acquire vev's during inflation, so there is no need to stabilize the extra
scalars which are always present in the theories with chiral matter multiplets.
The new class of models can describe any inflaton potential which vanishes at
its minimum and grows monotonically away from the minimum. In this class of
supergravity models one can fit any desirable choice of inflationary parameters
n_s and r.
