Preheat the oven to 350 degrees F.
In a small bowl combine the coriander, cumin, chili powder, pepper, and salt. Brush 1 tablespoon of the olive oil evenly over both sides of the tuna fillets. Sprinkle both sides of each tuna steak with the coriander mixture, gently rubbing the seasonings into the meat.
Heat the remaining tablespoon of olive oil in a large skillet over high heat. Add the tuna steaks to the hot oil and sear 30 seconds to 1 minute on each side. Remove the tuna from the pan and set aside.
Lay out 1 or 2 jicama slices, depending on the size. Top with some of the tuna and some of the guacamole and charred tomato pico. Fold into taco and eat immediately. Repeat with remaining ingredients.
*Jicama instructions: Slice off top and bottom of the jicama. Peel all of the skin off. Using a mandolin or a slicer, slice the jicama into very thin rounds (less than 1/16th inch).
Yield: 6 servings