  We study the electrodynamics of Dirac electrons in solids (e.g., bismuth) by
comparing it with quantum electrodynamics (QED). It is shown that Lorentz
covariance associated with the Dirac electrons in solids results in a
remarkable correlation between the dielectric and diamagnetic properties,
leading to a significant enhancement in the permittivity directly linked to the
well-known phenomenon of large diamagnetism.
