  The connection between $f(R)$ theories of gravity and scalar-tensor models
with a "physical" metric coupled to the scalar field is well known. In this
work, we pursue the equivalence between a suitable scalar theory and a model
that generalises the $f(R)$ scenario, encompassing both a non-trivial scalar
curvature term and a non-minimum coupling of the scalar curvature and matter.
This equivalence allows for the calculation of the PPN parameters $\beta$ and
$\gamma$ and, eventually, a solution to the debate concerning the weak-field
limit of $f(R)$ theories.
