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We study a modification of the Plebanski action, which genericallycorresponds to a bi-metric theory of gravity, and identify a subclass which isequivalent to the Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories.In this manner, scalar-tensor theories are displayed as constrained BFtheories. We find that in this subclass, there is no need to impose reality ofthe Urbantke metrics, as also the theory with real bivectors is a scalar-tensortheory with a real Lorentzian metric. Furthermore, while under the formerreality conditions instabilities can arise from a wrong sign of the scalar modekinetic term, we show that such problems do not appear if the bivectors arerequired to be real. Finally, we discuss how matter can be coupled to thesetheories. The phenomenology of scalar field dark matter arises naturally withinthis framework.

Scalar-Tensor theories from $\Lambda(\phi)$ Plebanski gravity