Deadlifts can leave you sore for days even when done with proper form and even when you do them on a regular basis. The lower back is one of the slowest muscle groups to recover and the deadlift is one of the most taxing exercises on the lower back. So, since you're new to deadlifting, I'm not surprised that you'd be sore for a long time.
That being said, I'll just bring up one other point: by working squats before your deadlifts, there is a form trap that's easy to fall into. Namely, you begin the deadlift by extending your legs without really lifting the bar enough which leaves you bent too far forward. Then, the rest of the deadlift becomes an almost stiff legged deadlift - often with a rounded back. I find that, after doing squats, I have to pay extra attention my form on deadlifts to avoid this problem. I wouldn't say to avoid this combination - just to pay extra attention to form!
Welcome to the joys (pain!) of deadlifting!