Electric Conductivity and Magnetic Susceptibility

  $$\sigma\propto (1-\chi_\text{v})$$

This means that diamagnetic materials are very good conductors of electricity; which they are.

As an example, the absolute value of magnetic susceptibility of silver is more than copper. So silver should be a better conductor of electricity (than copper); which it is.

By symmetry

$$\varsigma \propto (1-\chi_e),$$

where $\varsigma$ is magnetic conductivity.