Preheat oven to 350ºF. Lightly grease 9 x 5 inch or 8 1/2 x 4 1/2 inch loaf pan and set aside. In a large mixing bowl combine flour, baking powder, cinnamon, cloves, salt and nutmeg; whisk lightly to blend. In a medium mixing bowl beat together eggs, brown sugar and oil on medium speed until creamy. Beat in sweet potato until just combined. Add sweet potato mixture to dry ingredients in two batches, beating on low speed for about 1 minute after each addition. Mix just until blended. Fold in currants or raisins. Pour batter into prepared pan. Bake for about 1 hour, or until a tester inserted in the center comes out clean. Cool cake in pan, or wire rack, for 15 minutes. Turn onto rack to finish cooling.