While the chances of a continued war between the Western Allies that includes elements of the Wehrmacht and a Victorious Soviet Army are Highly unlikely, they are not impossible.
Let me suggest the following elements and ATL events of such a possibility. All have probably been gone over in great detail elsewhere:
1) The German Army, knowing that it is losing, manages to replace Hitler (say in mid 1944) and then puts it own person into power, and seek peace with both sides, going so far as to offer unilaterally to disengage. The allies to this point are determined to win an unconditional surrender and refuse, but the Western Allies at least consider it.
At the same time the German army closes all concentration camps and begins (as much as possible) to nurse the victims back to health. They do this because they know the camps will make a settlement more difficult.
2) The German Strategy then becomes one of ensuring the Western Allies take the largest share of Germany, while slowing the Russians down. Germany even begins to permit the healthier survivors of the holocaust to leave through Switzerland.
3) As a result, the German Armies in the West steadily retreat without a Battle of the Bulge or other attempts to stem the advance of the West. Western troops win lots of small engagements with hard core Nazi troops, (giving them a 'winning attitude'), but wide scale offenses are avoided.
4) The air war is deemphasized, and fewer attacks are made against the already shattered German Industry, almost all benefits of this are thrown against the Russians, who (quite naturally) resent the fact that the Western Allies have backed away from their destruction of Germany from the air.
5) The Yalta Conference is held on schedule, but now the Western allies are requiring all of Germany and Poland, leaving the Russians only East Prussia. Because of increasing reports related to Russian attrocities, this is widely backed by the US.
6) Stalin would (again quite naturally) resent this, and would order his troops to pull all stops in taking additional territory before the war's end.
7) Because of the more aggressive stance of the Russian Armies, numerous small flareups between Western and Russian Troops occur wherever they meet. Stalin is warned, and all aid to Russia is ended in late February. Because of the Greater German Resistance and industrial capacity (see #4 above) the Russian advance is much slower and by February has only reached the Vistula.
8) Western Reporters witness Russian attrocities against a fleeing German populace, including purposefull killings, rape and other attrocites against children. Horrific photoes of these events somehow make their way to the newspapers and are published. US public opinion begins to swing against the Russians. Even Great Britain begins to wonder about the wisdom of an unrestrained Soviet Army.
9) Germany again offers to surrender to the West pending negotiations, pleading that they are seeking protection from the Russians. The images of recent Russian attrocities are too fresh, and the Western Allies agree. Stalin is furious, threatening to take what he hasn't been given.
10) Russian troops attack Danzig, recently surrendered to English Troops who are int he process of demobilizing the remaining German Troops. The English troops resist, and a blood bath results with English and German troops fighting side by side against Russians. After several English transports arrive to evacuate their troops, and the German troops agree to fight the rear guard while the English are evacuated. The German die almost to a man, and the city is ransacked and looted.
11) English public opinion swings against the Russians. Stalin ignores warnings, and the alliance with Russia is formally ended by both the US and England. Neither English nor American troops bother to disarm surrendering German troops when working near Russian units, perferring instead to deal with these troops at and officer to officer level, and on occasion allowing them to remain in position against Russian troops.
12) Russian troops continue to advance into Polish territories, despite increasing protests. They arrive at Pozen where US armored forces have been demobilizing German Troops. General Patton, in response to Russian demands that he leave the city, answers "Nuts!" German forces are integrated into US forces in the resulting defense of the city.
13) In response to the attack, Engaland and the US declare an active state of hostility exists between them and Russia, while simultaneously accepting the formal alliance with the New German Republic in which the German Army remains intact.
14) March 4, 1944, The Soviet Union Declares War on all German Allies, including England and the US..