According to the declassified documents, a German intelligence officer reported to the CIA in March 1958 that Germany had known since 1952 that Eichmann lived in Argentina under the pseudonym "Clemens." The information was not entirely accurate, as the name Eichmann used at the time was "Clement."
However, the CIA chose not to make use of the information.
Israeli intelligence officers who have published their memoirs have written that Israel knew that Eichmann lived in Argentina by 1957, but lacked any information regarding his pseudonym.