Gold–aluminium intermetallic is a type of intermetallic compound of gold and aluminium which usually forms at contacts between the two metals. Gold–aluminium intermetallic have different properties from the individual metals, such as low conductivity and high melting point depending on their composition. Furthermore, Due to the difference of density between the metals and intermetallics, the growth of the intermetallic layers causes reduction in volume, and therefore creates gaps in the metal near the interface between gold and aluminium. The production of gaps lowers the strength of the metal compound, which can cause mechanical failure at the joint, fostering the problems that the intermetallics causes in metal compounds. These properties can cause problems in wire bonding in microelectronics. The main compounds formed are usually AuAl (white plague) and AuAl (purple plague), which both form at high temperatures, then AuAl and AuAl can further react with Au to form more stable compound, AuAl.