Dilute but significant: low cation concentration affects field dependent properties of Eu 2 Ga 11 Sn 35 .

We investigate the temperature and magnetic field-dependent electrical and thermal properties of Eu 2.2 Ga 11 Sn 35 , revealing a change in electronic structure and an increase in magnetoresistance with increasing field, as well as the origin of magneto-suppressed thermal conductivity of this unconventional inorganic clathrate-I material with very low cation concentration.