In a small bowl, combine the yeast and warm water, stirring till the yeast has dissolved. Cover and let rest for 5 to 10 minutes until frothy.
In the bowl of a stand mixer, combine the rye flour, sugar and yeast mixture. Stir till you have a soft, thick batter of sorts. Cover and let rest for 20 minutes, to allow the rye to absorb some of the moisture.
Now add the yoghurt, salt and all-purpose flour. Mix and then using the dough hook, knead on medium speed until the dough starts to pull together and become smooth. If doing this by hand, use a silicone spatula. The dough will become to ball up and then start to spread again, because rye flour doesn't have a lot of structure. Once it's relatively smooth (about 5 minutes) and you're able to stretch it without it breaking immediately, scrape it out into an oiled bowl. Shape into a round as best as you can, sprinkling a little flour on your hands to help you.
Cover the bowl with clingfilm and leave to rise for about 2 hours until doubled in size.
Now grease a 9x5 loaf tin and set aside. (Line it with baking paper for easy removal, then grease the paper as well. If you do use paper, some sticking of the bread is inevitable).
Punch down the risen dough, then using floured fingers, scrape it out into the prepared loaf tin. Don't worry about making it smooth or spreading it out, that will happen during the second rise.
Cover with clingfilm again, and leave for about 1 hour until doubled. Towards the end of the second rise, preheat the oven to 175 C.
Sprinkle the seeds on top of the bread (brush the top with a little water if they don't stick) and place on the lower rack in the oven. Bake for 35 to 40 minutes until browned on top, covering with foil if it's browning too quickly.
Set aside to cool for 10 minutes, then gently prise it out of the pan and leave to cool completely before slicing. Bread keeps well at room temperature for one night in warm areas, and in the fridge for 3 to 4 days after that. Happy eating!