In a large saucepan, cover potatoes with salted cold water by 1 inch and simmer, covered, until just tender, about 15 to 30 minutes, depending on size of potatoes. In a colander drain potatoes and cool to warm. With a sharp knife peel potatoes and cut cross-wise into 1/2 inch-thick slices.
While potatoes are boiling, prepare grill. In a small bowl whisk together oil, salt, jalapeno pepper and cumin and brush some onto both sides of potato slices, reserving remaining cumin oil. Grill slices on an oiled rack set 5 to 6 inches over glowing coals until golden brown, about 1 minute on each side, and transfer with tongs to a platter.
Thinly slice scallion diagonally and sprinkle over potatoes. Whisk lime juice into remaining cumin oil with salt and pepper to taste and drizzle over potatoes. Serve potato salad with lime wedges and sprinkle with coriander.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.