Oops your right. prestige paladin is in UA. But looking over him, this guy's nearly as topheavy.
Reqs:
Alignment: L-G
BAB: +4
Skills: Knowledge(religion) 2, Knowledge(nobility and royalty) 2, Ride 4
Feat: Mounted Combat
Spellcasting: Ability to cast protection from evil as a divine caster.
Special: Ability to turn undead
By 3rd level, this guy's got all palidin abilities except remove disease, and he increases his divine spells every other level. As set up, this increases the scope and power of the paladins's spells somewhat, but that's balanced by the fact that he doesn't get as many uses of smite and Remove disease as the base class.
As written, the only reason for a fighter to take leves beyond three is to get the (slightly better) spells instead of bonus feats. Worse, a cleric can take three levels in this class, get pretty much all of the paladin abilities, and only take a one-level hit in spells per day.
I prefer the warcraft version, the Paladin Warrior. He's also takable at 5th, but doesn't require any levels of divine caster. The prereqs are pretty tailored to the warcraft setting, but can easily be modified. Here's there ability progression:
1st: Lay on hands, detect outsiders/undead, turn outsiders/undead
2nd: Aura of Courage
3d: Smite oustiders/undead
4th: Divine heath, remove disease 1/day
5th: Divine Grace
6th: Greater turning, smite 2/day
7th: Extra turning
8th: Banishing Strike 1/day
9th: Smite 3/day
10th: Power turning
If you want a PrC paladin geared towards fighting undead and fiends, this one's definately the way to go.