  How particular bonds form in quantum materials has been a long-standing
puzzle. Two key concepts dealing with charge degrees of freedom are
dimerization (forming metal-metal bonds) and charge ordering (CO). Since the
1930s, these two concepts have been frequently invoked to explain numerous
exciting quantum materials, typically insulators. Here we report dimerization
and CO within the dimers coexisting in metallic NaRu$_2$O$_4$. By combining
high-resolution x-ray diffraction studies and theoretical calculations, we
demonstrate that this unique phenomenon occurs through a new type of bonding,
which we call Z-type ordering. The low-temperature superstructure has strong
dimerization in legs of zigzag ladders, with short dimers in legs connected by
short zigzag bonds, forming Z-shape clusters: simultaneously, site-centered
charge ordering also appears. Our results demonstrate the yet unknown
flexibility of quantum materials with the intricate interplay among orbital,
charge, and lattice degrees of freedom.
