Spy Tango. Martin Schuller, Spy Catcher, #2

Argentina, 1940 - where lovers dance the tango, and spies do a more dangerous dance... After disobeying orders from the Chief Special Agent, State Department counterintelligence agent Martin Schuller has been exiled to the American Embassy in Argentina, where he has to work with his FBI nemesis, Reginald Sloan. But if you're going to be sent into exile in 1940, Buenos Aires is a pretty good place to land.
When Martin discovers a Nazi smuggling operation sneaking war materiel from Argentine mines to the Third Reich, in violation of the Americas Security Zone, he gets back to pursuing Nazi spies. As the world teeters on the brink of Nazi domination, stopping the smugglers takes on new urgency. Can he help save the world without getting caught in dangerous local entanglements? And can he keep his children out of the middle of it?