Instead of yeast, it's the baking soda that leavens the loaves, activated by the acid in the buttermilk. (This recipe for brown soda bread also gets some added rise from baking powder.) ...
350g malted-grains, malted wheat-flour or Granary flour 'Put the flours, salt and bicarbonate of soda in a large bowl ... Put on the baking sheet and dust lightly with flour.