  We investigate a Lorentz invariant action which is quadratic in two rank-2
symmetric tensor fields in Minkowski spacetime. We apply a scalar-vector-tensor
decomposition to two tensor fields by virtue of 3-dimensional
rotation-invariance of Minkowski spacetime and classify theories with seven
degrees of freedom based on the Hamiltonian analysis. We find two new theories,
which cannot be mapped from the linearized Hassan-Rosen bigravity. In these
theories, the new mass interactions can be allowed thanks to the transverse
diffeomorphism invariance of action.
