  Ordered double perovskite oxides of the general formula, A2BB'O6, have been
known for several decades to have interesting electronic and magnetic
properties. However, a recent report of a spectacular negative
magnetoresistance effect in a specific member of this family, namely Sr2FeMoO6,
has brought this class of compounds under intense scrutiny. In this small
review, we present few theoretical and experimental results, describing mainly
the effects of Fe/Mo antisite defects on the properties of this compound and
also briefly discuss few other puzzling facts about this fascinating compound
