Peel and slice 1/4 pound of jicama into 1/4 inch thick bite-size pieces, and add to a big bowl. Stem, core, and halve a small fennel bulb. Slice 1/2 of it into thin half moons, and add. Slice 1/4 of a small red onion thinly, and add. Squeeze a small seedless tangerine over the jicama and fennel, sprinkle with 1/8 teaspoon salt and mix. Garnish with a little black pepper and a tablespoon of chopped fennel leaves.