BRASILIA, June 18 (Reuters) - Brazil's Superior Court of Justice ruled on Tuesday that steelmaker Ternium must pay 5 billion reais ($926.75 million) to CSN in a dispute related to Ternium's acquisition of a stake in local firm Usiminas. ($1 = 5.3952 reais) (Reporting by Ricardo Brito; Writing by Peter Frontini; Editing by Kylie Madry)