  The search for new materials with extremely high ("colossal") dielectric
constants, required for future electronics, is one of the most active fields of
modern materials science. However, the applicability of the colossal-epsilon'
materials, discovered so far, suffers from the fact that their dielectric
constant, epsilon', only is huge in a limited frequency range below about 1
MHz. In the present report, we show that the dielectric properties of
La15/8Sr1/8NiO4 surpass those of other materials. Especially, epsilon' retains
its colossal magnitude of >10000 well into the GHz range. This material is
prone to charge order and this spontaneous ordering process of the electronic
subsystem can be assumed to play an important role in the generation of the
observed unusual dielectric properties.
