  Motivated by Bryant's research on austere subspaces and Cartan's
isoparametric hypersurfaces with 3 distinct principal curvatures, we construct
three families of austere submanifolds with flat normal bundle in unit spheres.
From these examples we find three irreducible proper Dupin hypersurfaces with 5
distinct principal curvatures of different multiplicities. Moreover, as an
application, we obtain an upper bound estimate for the dimension of austere
subspaces.
