Line a loaf pan with plastic wrap. Be sure to leave plenty of plastic around the edges so they can be folded over to cover the top. Put the almonds in the bottom of the prepared pan in an even layer (this will eventually become the top, so make it look pretty!). Reserve.
Whip the cream with a whisk or an electric beater until it forms medium peaks. Refrigerate until ready to serve.
Bring a saucepan with about 1-inch of water to a boil, over low heat. In the metal bowl of a stand mixer, combine the 1 1/4 cups of sugar, egg yolks, lemon juice and zest and the pinch of salt. Whisk to combine. Put the metal bowl on the saucepan, and reduce the heat under the saucepan so the water is just at a simmer. Whisk the egg mixture until it gets very light and fluffy, this will take about 4 to 5 minutes. For an insurance policy you can take the temperature of this mixture. It should be about 165 degrees F on an instant-read thermometer. Put the mixer bowl on the mixer and beat with the whisk attachment until the mixture has doubled in volume and the bottom of the bowl is cool when touched.
Fold in the reserved whipped cream in increments. Do this gently but quickly. When it is a homogeneous mixture, pour it into the prepared loaf pan. Fold the plastic over the top and transfer to the freezer. Freeze at least 4 to 5 hours, but this can be done overnight or up to a couple days in advance.
Combine the oranges, mangoes, mint and remaining 1 tablespoon of sugar in a small bowl. Let the mixture macerate for about 1 hour before serving.
Remove the loaf pan from the freezer and open the plastic. Turn the semifreddo out of the loaf pan to a serving platter and remove the plastic. With hot knife, slice the semifreddo into 1-inch slices and garnish with the orange/mango salad.