In the framework of classical scale invariance, we consider quadratic
gravity in the Palatini formalism and investigate the inflationary
predictions of the theory. Our model corresponds to a two-field
scalar-tensor theory, which involves the Higgs field and an extra scalar
field stemming from a gauge U(1)(X) extension of the Standard Model,
which contains an extra gauge boson and three right-handed neutrinos.
Both scalar fields couple nonminimally to gravity and induce the Planck
scale dynamically, once they develop vacuum expectation values. By means
of the Gildener-Weinberg approach, we describe the inflationary dynamics
in terms of a single scalar degree of freedom along the flat direction
of the tree-level potential. The one-loop effective potential in the
Einstein frame exhibits plateaus on both sides of the minimum and thus
the model can accommodate both small and large field inflation. The
inflationary predictions of the model are found to comply with the
latest bounds set by the Planck collaboration for a wide range of
parameters and the effect of the quadratic in curvature terms is to
reduce the value of the tensor-to-scalar ratio
