Binary mixture of undecyloxy cyanobiphenyl (11OCB) and 4-n-pentyl phenyl-4-n'-hexyloxy benzoate (ME6.05) shows enhanced smectic A phase, where 11OCB has smectic, A and ME 6.05 has nematic phases. We report here the phase diagram, refractive indices, densities and orientational order parameters of different binary mixtures of 11OCB + ME6.05 throughout the entire composition range. At a reduced temperature, density values increases with mole fraction (x) of 11OCB up to x = 0.25 and then decreases continuously having a minimum near x = 0.8. The birefringence and values follow the same trend showing a maximum near x = 0.4 and a minimum near x = 0.8.