Unique Loop Type 4
Use solution uniqueness and a strong link within a loop to eliminate the other candidate that would create another solution.
All candidates have been entered in the empty cells.
Assume that the puzzle has a unique solution. Candidate 5 has only two possible places in A. If candidate 6 is true at one place in A, candidate 5 is true at the other. Therefore, the two loop digits can swap into another solution. That contradicts uniqueness. Candidates 6 marked × can be removed.