Address them as you normally would, using the second output (the index of the first occurrence of the maximum value) from the max function:
[aa,bb,cc] = deal(3,5,7); % Assign Variables
Pop.A=[aa bb cc];
Pop.B=[ 2 4 6];
[Bmax, Bidx] = max(Pop.B);
Amatch = Pop.A(Bidx)
Amatch =
7
