The Minimal Polynomial of a Riemannian C_0-Space

We construct, at each point of a Riemannian C_0-space, a polynomial in one variable whose coefficients are polynomial functions on the tangent space. For a homogeneous Riemannian C_0-space (for instance, a G.O. space) these pointwise-defined polynomials glue together to a global polynomial whose coefficients are Killing tensors invariant under the full isometry group. Moreover, the degree of this polynomial provides an upper bound for the Singer invariant of the space.