In a paragraph about a paper, where do I put the citation?
I feel that it is best to cite once for each unique referent. In your case, you are referring first to a set of methods, and later to a result. Thus I would write


  The Harman method (Harman, DATE) was devised by T. C. Harman .... steps to complete
  the method .... Harman showed that ZT could be computed from eq. (2.1) (Harman, DATE)