We present the phase diagram of a binary system of two nematogenic terminal, non-polar compounds in which an induced smectic A phase appears over a large concentration–temperature range. X-ray measurements give evidence that the layer spacing,d, of this induced smectic A phase is clearly larger than the average molecular length,L(d/L:112 … 1.23). The unusual experimental results are interpreted on the basis of a pronounced steric interaction by which gaps between the large double swallow-tailed compounds are filled with small molecules. We propose theterm filled smectic A phasefor this new type of induced phase.