a-Axis oriented films of the TlBaCaCuO family have been grown on LaAlO 3 (100) buffer layers on SrTiO 3 (100) substrates. The two step fabrication procedure involves the deposition of BaCaCuO(F) matrices through metal-organic chemical vapour deposition (MOCVD) and their annealing to yield the TlBaCaCuO phase through a thallium vapour diffusion process. The present unusual orientation, which to our knowledge is the first example of an a-axis orientation for this class of superconductors, is due to the nature of the LaAlO 3 buffer layers deposited on SrTiO 3 (100) substrates. The LaAlO 3 films deposited in-situ via MOCVD from the new generation precursor La(hfa) 3·diglyme (hfa=1,1,1,5,5,5-hexafluoro-2,4-pentanedione, diglyme=bis(2-methoxyethyl)ether) and Al(acac) 3 (acac=acetylacetone) are highly (100) oriented. The full widths at half maximum (FWHM) of the rocking curve of the (100) peak as small as 0.16° have been observed.