The man and woman helped run an international romance scam that used bogus profiles on dating websites to woo dozens of victims into giving up more than $US6 million ($A8.7 million), federal prosecutors say.
Mr Inalegwu, 31, made his initial court appearance late on Tuesday but 24-year-old Ms Mathieu remained at large yesterday.
Authorities have identified more than 33 victims, who sent more than A$8.7 million overall to the conspirators, including A$4.1 million that was sent directly to Mr Inalegwu and Ms Mathieu.
The couple allegedly spent the money on personal expenses, transferred money to other bank accounts they controlled and moved funds to bank accounts held by conspirators in Nigeria and Turkey.
The conspirators made initial contact with alleged victims through online dating and social media websites, then corresponded with them via email and phone, authorities said.
They allegedly used fictitious identities and pretended to strike up a romantic relationship with them and asked the victims to send money to them, or their associates, for fictitious emergency needs.
The conspirators also defrauded people by allegedly advertising properties they didn’t own and collecting application fees and security deposits on those properties, authorities said.