  Owing to the chirality of Weyl nodes characterized by the first Chern number,
a Weyl system supports one-way chiral zero modes under a magnetic field, which
underlies the celebrated chiral anomaly. As a generalization of Weyl nodes from
three-dimensional to five-dimensional physical systems, Yang monopoles are
topological singularities carrying nonzero second-order Chern numbers c2 = +1
or -1. Here, we couple a Yang monopole with an external gauge field using an
inhomogeneous Yang monopole metamaterial, and experimentally demonstrate the
existence of a gapless chiral zero mode, where the judiciously designed
metallic helical structures and the corresponding effective antisymmetric
bianisotropic terms provide the means for controlling gauge fields in a
synthetic five-dimensional space. This zeroth mode is found to originate from
the coupling between the second Chern singularity and a generalized 4-form
gauge field - the wedge product of the magnetic field with itself. This
generalization reveals intrinsic connections between physical systems of
different dimensions, while a higher dimensional system exhibits much richer
supersymmetric structures in Landau level degeneracy due to the internal
degrees of freedom. Our study offers the possibility of controlling
electromagnetic waves by leveraging the concept of higher-order and
higher-dimensional topological phenomena.
