Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Peel and dice the sweet potato into 1/2-inch cubes, then toss them with 0.5 tablespoon of olive oil and a pinch of salt and pepper.
Spread the sweet potatoes on the baking sheet and roast for 20 to 25 minutes until they are tender and caramelized on the edges.
While the potatoes roast, finely mince the garlic and fresh rosemary.
Season the chicken breast evenly on both sides with the remaining sea salt and black pepper.
Heat the remaining 0.5 tablespoon of olive oil in a stainless steel or cast iron skillet over medium-high heat.
Place the chicken in the skillet and sear for 5 to 7 minutes per side, or until the internal temperature reaches 165°F.
During the last 2 minutes of cooking, add the minced garlic, rosemary, and the juice of the half lemon to the pan, spooning the juices over the chicken as it finishes.
Steam the broccoli florets for 4 to 5 minutes until they are bright green and tender-crisp.
Plate the lemon-herb chicken alongside the roasted sweet potatoes and steamed broccoli, drizzling any remaining pan juices over the chicken before serving.