An example of compact K\"ahler manifold with nonnegative quadratic bisectional curvature

We construct a compact K"ahler manifold of nonnegative quadratic bisectional curvature, which does not admit any K"ahler metric of nonnegative orthogonal bisectional curvature. The manifold is a 7-dimensional K"ahler C-space with second Betti number equal to 1, and its canonical metric is a K"ahler-Einstein metric of positive scalar curvature