The intermetallic compounds of the alkali metals with the heavier group 13 elements (aluminium, gallium, indium, and thallium), such as NaTl, are poor conductors or semiconductors, unlike the normal alloys with the preceding elements, implying that the alkali metal involved has lost an electron to the Zintl anions involved.
ðɪ ˌɪntɚmətˈælɪk kˈɑːmpaʊndz ʌvðɪ ˈælkəlˌaɪ mˈɛɾəlz wɪððə hˈɛviɚ ɡɹˈuːp θˈɜːtiːn ˈɛlɪmənts ˌæljʊmˈɪniəm, ɡˈæliəm, ˈɪndiəm, ænd θˈæliəm, sˈʌtʃ ɐz nˈɑː tˌiːˈɛl, ɑːɹ pˈʊɹ kəndˈʌktɚz ɔːɹ sˌɛmɪkəndˈʌktɚz, ʌnlˈaɪk ðə nˈoːɹməl ˈælɔɪz wɪððə pɹɪsˈiːdɪŋ ˈɛlɪmənts, ɪmplˈaɪɪŋ ðætðɪ ˈælkəlˌaɪ mˈɛɾəl ɪnvˈɑːlvd hɐz lˈɔst ɐn ᵻlˈɛktɹɑːn tə ðə zˈɪntəl ˈænaɪənz ɪnvˈɑːlvd.