Preheat oven to 350°F with rack in middle.
Stir together sugar, butter, brandy, and extracts in a large bowl, then stir in almonds and eggs. Stir in flour, baking powder, and salt until just combined.
Using moistened hands, halve dough and form 2 (16-by 2-inch) loaves on an ungreased large baking sheet. Bake until pale golden, about 30 minutes.
Arrange biscotti, with a cut side down, on a clean baking sheet and bake until golden, 20 to 25 minutes. Transfer to rack to cool completely.