Wash the sweet potatoes, cut them into slices about 1 cm thick and place them on an oiled baking tray. Sprinkle with 2 tablespoons of oil and season with salt. Grill under the hot oven grill on the second rail from above for about 20 minutes, turning once.
Peel garlic and chop finely. Mix with lemon juice, 1⁄2 tsp salt and pepper. Fold in 5 tablespoons of oil. Chop the almonds coarsely. Wash coriander, shake dry. Chop leaves and stems finely.
Arrange sweet potatoes with yoghurt, almonds, coriander and lemon oil.