Since most modern republics, including the United States, are representative by nature (meaning citizens elect representatives to govern), using the term "representative republic" can seem a bit repetitive. However, the term highlights both the nature of the government (a republic, with no monarchy) and the specific method by which it operates (representative democracy).
So, while "representative republic" isn't redundant, it's somewhat descriptive of the dual aspects of governance—both emphasizing the lack of monarchy (republic) and the representative system (democracy).
^^^Here is what I found... we may both we right...