South Korea's top carmaker, Hyundai Motor Co., and its smaller affiliate, Kia Motors Corp., saw sales of their mid-size cars in China expand in the first quarter of this year on efforts to sell more pricey cars to improve profitability, data showed Sunday. Of the 440,514 vehicles the two carmakers sold in the January-March period in the Chinese market, the share of cars in the mid-size segment came to 81,311 units, or 18.5 percent, according to industry data.