If you pass 이자 (alone or attached to a noun) to Google Translate or Naver Translate, they both translate it as "interest" but the same two apps also use it as a particle (a postfix) that seems to mean "and" or "as well". My (italian/korean) dictionary just define it as "interest".
See this sentence (that is my first attempt to describe myself to a korean friend using Naver Translate):
저는 분석 화학자이자 컴퓨터 프로그래머입니다.
Is this particle actually used to mean "and" or "as well"?