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The ternary crystal structure R₅Co₂Ge₃ was discovered in 2017 [1]. When R is moment bearing, the low-temperature magnetic state(s) can be complex. For non-moment bearing R=La, the situation is simpler and intriguing; La₅Co₂Ge₃ is a small moment, itinerant ferromagnetic compound having a transition temperature of 3.8K and an effective moment of 0.1µ_B [2]. In order to better understand the nature and possible tunability of this ferromagnetic transition, we report the substitution of Co with Ni, Fe and Rh as well as Ge with Si. Single crystals of La₅(Co_1-xA_x)₂Ge₃ (A=Ni, Fe, Rh) and La₅Co₂(Ge_1-xSi_x)₃ were grown and characterized by magnetic and transport measurements. A comparison of the transition temperature, magnetic and transport properties will be discussed.

[1] Q. Lin, et al., Chem. Eur. J 23,10516 (2017) [2] S.M. Saunders, et al., PhysRevB 101, 214405 (2020)