Note that much more samples were synthesized and analyzed than listed herein. Therefore conclusions made in the manuscript are not only based on these samples.

Sample ID	Precursor Sn:Zr:Se (at.%)	Transport agent, g	Ampoule position	ramp1, h	temperature1, oC	duration, h	temperature2, oC	ramp2, h
K1b			0.96:0.96:3.1			None		Vertical		  4		 625			 80		 400			 8
K1			0.96:0.96:3.1			None		Vertical		  4		 700			 24		 600			 60
K1I1			0.96:0.96:3.1			SnI2, 0.01	Vertical		  4		 710			 10		 600			 55
G1I1S2			1.04:1.04:2.9			SnI2, 0.01	Horizontal		  4		 740			 60	         550			 24
G1I1S3			1.09:1.09:2.8			SnI2, 0.01	Horizontal		  4		 740			 60		 550		 	 24
G1I1S4			0.92:0.92:3.2			SnI2, 0.01	Horizontal		  4		 740 			 60		 550			 24
F1I1s_OG		0.98:0.98:3.05			SnI2, 0.01	Horizontal		  3.5		 700			 59		 500 			 30
L1I1e			0.98:0.98:3.05			SnI2, 0.01	Horizontal		  7		 700			 57		 100			 7
L1I1c			0.98:0.98:3.05			SnI2, 0.01	Horizontal		  7		 700			 35		 100			 7
L1I1f			0.98:0.98:3.05			SnI2, 0.01	Horizontal		  7		 700			 24		 100			 7