Are a substance's electrical and heat conductivity related?

[ScientificMind]

For example can an object be very conductive to electricity but be a very poor conductor of heat and vise-versa, or is a good conductor of one always a good conductor of the other and a bad conductor of one always a bad conductor of both?
If they are related, then how and why are they connected?
If they are not related, then what differences allow the two properties to be independent of one another?

 

[mfb]

In solids, they are closely related. In liquids it is more complicated.

Thermal conduction happens both via electrons and atoms, while electrical conduction is limited to electrons. Every good electrical conductor will also conduct heat, but there are some electrical insulators that still have a good thermal conductivity, like diamond.
As usual, Wikipedia has a list.