The compounds crystallizing with the Cr5B3 structure type can be divid
ed into two isopointal subfamilies. The two binary compounds Tl5Te3 an
d Tl5Se3, which belong to the minor subfamily, the so-called In5Bi3 su
bfamily, differ in some structural details and exhibit different physi
cal properties. The effect on substituting part of the thallium atoms
by other metals M' and part of the chalcogen atoms by halogens has bee
n studied. Crystal structures and physical properties (resistivity, su
sceptibility, T-c) of some ternary derivatives are reported.