Is there any implementation for handling such a large matrix to give us A, IA and JA, without having have to slurp all the files into RAM?

As you describe A, IA and JA, it seems to me that each of them can be created by just scanning the matrix top to bottom; left to right. Since that means never having to slurp in more than the length of an element, I don't see why you would have to slurp in the file into memory.

Now, you still may have so many non-zero elements such that you don't have memory enough for A, IA and JA, but that's a different matter.

BTW, are you really counting starting from 1?