Jonathan Toebbe, who worked as a nuclear engineer for the US Navy, and his wife Diana -- both in their forties -- were arrested by Federal Bureau of Investigation agents on Saturday and charged with violating the Atomic Energy Act in a criminal complaint, the Justice Department said in a statement.

For nearly a year, the couple "sold information known as restricted data concerning the design of nuclear powered warships to a person they believed was a representative of a foreign power," the statement said, adding that the recipient of the information was, in fact, an undercover FBI agent.

Jonathan Toebbe, who had access to restricted data on nuclear-powered warships through his work, collaborated with his wife to exchange data on submarine nuclear reactors for around $100,000 in cryptocurrency, the complaint affidavit alleges.

The affidavit says Toebbe in April 2020 mailed a package to a foreign government "containing a sample of restricted data and instructions for establishing a covert relationship," according to the statement.

The couple in following months transferred multiple SD cards of data to the agent, who was posing as a representative of the foreign government, including by hiding them in half a peanut butter sandwich and a chewing gum package left at agreed locations.

US Attorney General Merrick Garland praised the agencies involved for "thwarting the plot" and "taking this first step in bringing the perpetrators to justice," the statement said.

The couple is due to appear in West Virginia federal court on October 12.