Preheat the oven to 180C and line a loaf tin with parchment paper.
In a small bowl mix together the flour, baking powder & ground ginger. In a medium bowl, cream the margarine. Add the syrup, yogurt and flour mixture, and stir until combined. Fold in the sweet potato and pour into the loaf tin.
Bake for 40-50 minutes before leaving to cool.
While the cake is cooling, melt together the creamed coconut and maple syrup. Remove from the heat and add the lemon juice and zest. Ice the cake before serving.