During a cruise flight at 10,600 meters, an emergency descent was initiated due to a fire detected in the rear cargo hold. The APU fire warning activated, followed by the DC electrical system failure, impacting navigation, compass, and flap systems. The aircraft landed in a snow-covered field, resulting in collision with irrigation equipment and aircraft breakup. The probable cause is an in-flight fire originating in the underfloor area of the cargo hold, likely caused by a short circuit in the electrical wiring.During a cruise flight at 10,600 meters, an emergency descent was initiated due to a fire detected in the rear cargo hold. The APU fire warning activated, followed by the DC electrical system failure, impacting navigation, compass, and flap systems. The aircraft landed in a snow-covered field, resulting in collision with irrigation equipment and aircraft breakup. The probable cause is an in-flight fire originating in the underfloor area of the cargo hold, likely caused by a short circuit in the electrical wiring.