I am interested in to undrestand when the Minkowski units in real biquadratic number fields are minimal in the log unit lattices. I have read some pieces of literature online which are investigating this question in the case when the number fields are totally real and cyclic with a low prime degree or the degree is 4 or 6 by studying their Galois module structure. I really appreciate it if someone could introduce some literature or possible approaches to this problem.
I also asked this question in https://mathoverflow.net/questions/453461/condition-on-the-minimality-of-minkowski-units