By substituting Si- with (Al-H)(-) in trigonal BaSi2, a series of hydrides has been synthesized with compositions BaAl2-xSixH2-x (0.4 < x < 1.6). OFF calculations show that the end compositions BaSi2 and BaAl2H2 are conductors whereas the intermediate BaAlSiH is a semiconductor. The cell parameters for the trigonal cell vary linearly as a function of the Si-/(Al-H)(-) substitution in this MgB2 related structure type, opening up the possibility of continuously tunable electric properties.