Help a beginner out: biking without sabatoging weight lifting?

I'm currently lifting weights about 4 days a week. However, I love biking, both steady state (40-60 minutes) and in interval-style intensity (20 minutes). However, I've been told that biking in my off days or after my strength training will impede the muscle growth I'm trying to achieve with the weights. Is this true? How can I bike (and lose some fat, hopefully) without detracting from the process going on with weights?

Can I just do 20 minutes of intense biking after non-lower-body strength training? How about biking in the mornings and lifting in the afternoons 3 days a week, and leaving the off days free of exercise? Also, what should I do nutrition-wise in between to make sure both are getting their due?

I'm a beginner (about 2 months of lifting) so I'd really appreciate any help. Thanks!
 
I trail ride a lot. I lift 3 days a week and ride the days I don't lift. If you do both in one day I'd lift early and ride later.
 
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