We report on neutron diffraction measurements on the equiatomic liquid alloys K-Sb, K-Bi, and Rb-Bi up to temperatures of T=1800 K. The prepeaks in the resulting total structure factors S(Q) are indicative of intermediate range ordering. The shift of the prepeak positions towards smaller momentum transfer Q with increasing temperature suggests increasing distances between the structural polyanionic units. From reverse Monte Carlo (RMC) simulations the prepeak is assigned essentially to correlations between the polyvalent metal atoms (Sb or Bi), remaining even up to the highest temperatures measured. The simulations lead to models exhibiting Sb (or Bi) atoms clustered in short chains and dumbbells rather than in higher coordinated clusters or networklike structures.